BACK UP YOUR FILES BEFORE REPLACING - I recommend using https://www.gta5-mods.com/tools/emfsp-easy-mod-folder-for-sp-player-mods to modify clothes and accessories easily

For a basic install copy all files (except for the prop mask) to:
mods/x64v.rpf/models/cdimages/streamedpeds_players.rpf/player_two (folder)

For the mask prop install the p_head files into: mods/x64v.rpf/models/cdimages/streamedpedprops.rpf/player_two_p