Copy ALL your photos to an external hard drive. After MAKING SURE they are OK (extremely important) on the external you can delete them from the internal drive and also remove them from the trash. You should also have a backup of these photos on another external drive. You then should be able to use Lightroom.
I purchased Lightroom so that I could move all of my photos out of their various storage locations, such as iPhoto and Photos folders while simultaneously freeing up much needed space on my harddrive.
That's an awfully expensive program to perform a move. Don't you plan on using Lightroom for some other purpose?
The instructions to do this move in Lightroom are in this document, scroll down to "Part 2 — Updating Folder Location" and begin there.
I'm sure there are other ways that I will use it, but I've been managing using iPhoto for a long time and now I have photos in three different directories and I can't access any of them at the same time and it's all a mess. So I thought that switching to a better program that had built in editing and processing as well as photo management would let me put it all together in the (hopefully) least resistant to corruption way. But I do feel like I'm throwing money at a problem that doesn't seem to go away. I thought the AirPort Time Capsule would solve my storage issues, but now it looks like I'm going to need a different large drive to hold my photos since Lightroom doesn't like it. If you have any better ideas I'm open to them.
So I thought that switching to a better program that had built in editing and processing as well as photo management would let me put it all together in the (hopefully) least resistant to corruption way.
Lightroom (and any software) does not manage or organize your photos for you. You must cause the organization, or management to happen by giving Lightroom instructions. Lightroom won't magically make you more organized.
So, if "it's all a mess", it is because you haven't put the effort into your existing software to cause this organization to happen. Lightroom won't help unless you put the effort in. You can put the effort into organizing your photos using your existing software just as easily and effectively as you can do it in Lightroom. But you are right, throwing money at more expensive software won't solve the problem of organization.
but now it looks like I'm going to need a different large drive to hold my photos since Lightroom doesn't like it.
I don't know what this means or why Lightroom doesn't like it, but Lightroom can work with photos on any hard drive or network drive. If it's not working, you have to explain what is happening and we can probably tell you how to make it work.
When I try to create the catalog it says I can't use a network drive or a removable drive. So I'm not sure where I'm supposed to store my photos other than a new external drive that I can plug directly into my computer instead of using the wireless/network drive.
And yes, obviously I have to manage the files, and I did that quite well within iPhoto, but then they switched to Photos and created a new photo library instead of using the one that I had that was full of my pictures, so now everything is split up and I want to consolidate it all together, which is going to require manually pulling photos out of the iPhoto directories, and since I don't like that way of saving my photos and don't want to use the Apple programs anymore I needed a different type of software, which is where Lightroom came in. It was one of the recommended applications for not corrupting your photos I found on multiple sites.
But yes, I was definitely confused that it is a subscription based service and not just a program that I can install and use. But I can't find really find any other programs that Apple photos and Picasa recommended for the same services. If there's another program that is cheaper or a one-time pay I would happily use it. I would keep using iPhotos if it didn't keep all my photos in that directory, but it's so inaccessible with the amount of photos I have.
The catalog can be created on any hard drive that is connected directly to the computer. This includes external hard drives. It DOES NOT include network drives. The Lightroom catalog cannot be on a network drive. If you are having difficulty creating a catalog on an external hard drive that is connected directly to your computer then there is something else wrong. Like (perhaps) you don't have both read and write permissions for that hard drive.
It sounds to me like your fundamental problem is dealing with files on your computer and how to create some space on your main disk. One of the major disadvantages of using iPhoto and such is that it hides your images in a hidden folder structure on your hard disk and it also tends to generate duplicate images all over. It also cannot deal with offline storage very well and so it tends to lead to full hard disks very quickly. This is especially true as Apple sells lots of computers with very inadequate internal hard disks and no way to upgrade them as they are soldered onto the motherboard. Now if you start using another program such as Lightroom or Picasa and import in that, you will generate lots of duplicates so you really need to understand what you are doing. You also need to figure out how to get your images on external hard disks if your internal hard disk is small. The main reason is simply that digital imaging costs hard disk space. This is all doable but takes some planning. There are many tutorials on the web on how to do this such as this one: How do I move only my photos to another hard drive, leaving the catalog where it is? - The Lightroom Queen
However, it sounds like even before you start using Lightroom your hard disk is already full, so you need to first free up some space to begin with.