Insane already posted this ages ago.
You need skinedit.
Download below when someone approves it.
So, when you download it, place all of it into a new folder.
So, you see 2 folders, correct?
Parts= Just parts of the character you can use.
Backgrounds= The background your going to use when your making it.
Open MCSkinEdit, press yes on everythin'
So..
now your on Skinedit!
You can see what your character looks like in the bottom right corner of it...
At the top you can customize it, note how it says; Face Left Back.. etc.
Just experiment.
When your done Save it in desktop or something, then can upload it to your minecraft account.
At Minecraft
Choose the pic you want to upload, then press save.
Congrats on your new skin!
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Insane already posted this ages ago.
lolsorry.
/requestclose
Sorry, I was thinking of that, but incase someone doesn't know how to use the search...