Can you change the permissions on that external hard drive?
I am not sure. I looked but couldn’t find where it was located. My husband seems to think I am going to need to format this external drive to be compatible with the Mac. Only problem is this is where I store all my images and that would mean I would have to move them or back them all up somewhere else. I am a little scared to do that.
it would be important to know in which format the external hard drive is formatted. For this purpose, select the external hard drive and choose from the context menu the word "information". Search "Format" there you can find the needed information.
OSX is not able to write to a NTFS formatted hard drive without tools, and I suspect that your hard drive is formatted as a NTFS. Mac can only read but not write it in the standard. In order to ensure that this works, you need an additional software. Apple itself has installed, writing to NTFS, indeed! But it's not enabled. With this program you can unlock it: NTFS-3G for Mac | MacUpdate. Here for the "safety" my link leading to a German website: