1. Launch OpenIV (go to http://openiv.com/ if you don't have it yet)
2. Turn on edit mode by clicking the "Edit Mode" icon in the top right.
3. Copy uppr_diff_XXX_X_uni.ytd. and paste it into  GTA V / x64v.rpf / models / cdimages / streamedpeds_players.rpf / player_one 
4. Turn off edit mode by clicking on the "Edit Mode" Icon for a second time.
5. Enjoy :)