Remember that 7Zip file? Drag the zip file directly into that folder with the plus icon, the one that's on the right side of the rocket icon as shown here.
This is where you drag the P5EX.7z file into.
This should bring up P5EX in the package list. Under the Enable column, make sure that you checked off the box for P5EX.
Note: If you have other mods before this, make P5EX at the top of the list. It takes the highest priority.
