first you need to download the wc3viewer from the tools section. in the tree view select your blp file(skin file). afterwards go to current file->extract blp. extract it as a TGA file. edit the skin with paint shop pro or photoshop. then in the veiwer, go to convert files, then convert the TGA file into a blp. afterwards import the skin into your map based on the path of the unit(youll find the path in the viewer based on what ou pulled down from the treeview).
