How to add a texture with transparent parts in wow need help.

[hangun]

so..i got this long robe model and texture from wow...and i edit it with ps. to make it shorter or making holes in it or w.e..i erased the parts that i need and i save it as.png but when i import it in wow...the parts that i erased are coverd with skin texture..X_X and i import the modify texture in wow as.. .png as .tga with alpha and as .blp with alpha..nothing is working...i dont know what else to do..so please i need help..if someone can help me with this.