Change cXX into whatever slot you want it to. Ex: c08 for slot 9  
Place the cXX into captain falcon's body folder. Skin might need to be TexID. Might be set to 32 I believe.
Place the chr_13_captain_xx into ui/replace/chr/chr_13. Be sure to chance the xx to the slot the skin is in. 
Ex: chr_13_captain_09 for slot 9

Credits to Tophick for Csp