Hey there, first congrats on successfully making your repair. It can be tricky.
The wifi antenna is in the top left corner of the touch. Its a goldish ribbon cable that kind of looks like a boomerang. It's glued to a piece of foam on the logic board and often sticks to the back of the digitizer when its removed.
It travels toward the left side and then turns and goes down behind the logic board just above the volume controls where it snaps on to a coupler/stud/receiver.
Be very careful not to tear the volume ribbon cable when prying up the logic board to snap it back on if that's the problem.
As with many things in the Ipod repair game, you kind of need to be an octopus to snap it back on without removing the logic board. Have an extra set of hands help if available.