Need help with Bit Locker

This edition (Ultimate) has Bit Locker as an option, in fact it's the only reason that I wanted it over Pro. I have created the "key", and stored it in my external drive. Now, I don't want to make any mistakes here, as I'll be locked out of my computer if I do. I see the four options where to "turn on" Bit Locker, both Windows drives, my recovery partition, and my external backup drive. When I enable the protection, what happens, and what do I need to do get back in? I think I know the answer (I had to create a password), but I just want to make double sure, before doing anything.

If its your first time using Bit Locker maybe try it on a Flash Drive first Cat ... like the old saying practise makes perfect