Hey,
It was definitely a lot simpler than I thought, and more stressful figuring it out than it should have been
Anyway, you go to Preferences, then click Audio Units Manager.
It may take a few tries, but in the list that appears in the pop-up window, check that iDrum is somewhere on that list. Probably at the very bottom.
After that, quit and restart Logic Pro.
In your New Project, add a "Software Instruments" track.
In the library that opens to the right on the screen, go to My Garage Band Settings. It should be right in that list, maybe the only plug-in in that folder.
I used Garageband originally, then started using Ableton Live and got Logic Pro just recently. iDrum was a necessity with Garageband, and it's just as useful in Logic Pro. I love Ultrabeats, but iDrum is just so much simpler IMO.
Hope this helps. Cheers.