What do you mean?
If you did a 109F4 skin for instance, you just create a new folder within your skins folder and add a number to it.
The first 109F4 skin you do would be named 109f41 the next would be 2, 3, 4 etc....
put your bmps in that folder. then create a txt file named the same 109f41 and type a brief descriptiion of your skin.
Make sure your bmps are 8/256 or they will crash the game. Get the "bright" it does a great job of reducing bmps to 8/256 with out pixelation.
Start ah2 go offline select 109f4 from the clipbaord and at the top there will be a skins drop down menu. Select the skin and spawn.
Hit f3 then f8 and zoom in and look around. You may need to adjust th lighting (by adjusting the time) to get a good look at various angles.
