Moving the catalog is really simple.
On the new drive, using Finder, create a folder to put the catalog in. Make sure you have READ and WRITE permissions on this folder and its parent.
Using Finder, copy your catalog from is current location to the new folder.
Optionally, copy the preview folder from the old drive to the same new folder as the catalog was put in. If you don't copy the preview folder, LR will recreate it.
If you did a COPY (as opposed to a MOVE), when you open LR, you will need to tell LR to use the new catalog location via the "open catalog" menu command. (As a Windows user, I am not sure what that looks like on the Mac.)