ENABLE EDIT MODE!!

everything Goes into into 

"x64v.rpf/models/cdimages/streamedpeds_players.rpf/player_zero" (Player zero is  michael)


Search and find each body part and left click, then replace then double click the file to check it's there 
you should see the new spiderman texture in there for each part, press "save" at the bottom then rebuild

if certain bits of the spidey costume aren't loading Drag in the parts individually and rebuild after eachone  