/skin

Citizens on the WCF Modded server can use chat command /skin to open the "skin box". When used, a blank inventory will appear on the right. Drag a skinnable item of yours into the empty box and it will begin to populate all the server's available skins for that item. It may take several minutes to load the thumbnails the first time and it may require several attempts to load thumbnails of all skins for some item types. This is due to a limitation in Rust.

simply either right-click or drag out the item that has the desired skin and the box will close and you will now have a skinned item!