To get images into Lightroom, you have to import them.
You can import them directly from the external drive, but to to be able to work on them, the drive has to be connected.
To start working, either go to File > Open, and navigate to the catalog file, or double click the catalog file to launch Lightroom.
Then click Import, and import your files using the Add option at the top of the import screen.
You may find this article useful: Lightroom basics
Thank you for your response. Once I import them, it will take space of my internal hard drive, correct? If so, Can I move them to the external drive again so I can free up memory on my computer? or what would you do?
Importing the images from the external hard drive does not put them on your internal hard drive. The import process is simply one of showing my room where the images are located. There is a previews folder on your internal hard drive that works together with your catalog. But the images themselves will remain on the external hard drive. You can choose to put your catalog on the external hard drive as well.
Imported images are not "in" Lightroom, they remain in their original location, and are only referenced by the catalog.
Lightroom will create previews, that will take up quite a lot of space.
But in your case they will also be on the external disk, in the same folder as the catalog.
I suggest you read the article I linked to - it could save you some frustration ...
Yes, if your images and your catalog are both on the external hard drive then all of your photo work will remain on that external hard drive. Lightroom does not consume copies of your images. It merely points to them at their folder location.
So. The catalog that I use to have on the external hard drive (two files, 1. Lightroom5catalogpreviews.lrdata file and 2. Lightroom5catalog.lrcat file) can I delete those files and use the newly ones created on my internal HD after I import the photos from my external HD?
Sorry for so many questions. Just wanted to get this right.
Thanks to all for your invaluable help.
You don't need to create a catalog on your internal drive.
Just double-click the .lrcat file on the external drive to get started.
Since you already have a catalog file, it might contain some previous work?
I really never used or work with that catalog. I really want to start working with a clean catalog and start organizing all of my photos. What would be the best way to do so?
In that case, double-click the old catalog to launch Ligtroom.
Then go to File > New Catalog, which will let you create a new catalog in the location of your choice, like somewhere on your external disk.
Give it a unique name, one that you will remember.
Using Windows Explorer or Mac Finder you can now delete the folder containing the old catalog.