@peanut wagon
You need to add the APC20 device in environment of Logic, see click & ports layer. You need to split the channels to 8 of there own, channel splitter. Then cable the first 8 to the 8 channel strips in Logic. There is more detail to it than this, but if understand the environment, pretty easy. I use my old Yamaha O1v digital mixer as a control surface, since it has midi. Building a custom environment for all my devices was the way to go for me.
I wish I could get Logic to talk back to the APC40/20 and my O1v. Some of the hacked user modes on my APC40 would be killer to use in Logic.