❓ How to create skin

Hey could someone please tell me how to make skin for my alredy existing account.
Soo my name in minecraft is RedUnnamedPlayer and I want to make skin for it but currently its steeve is it posible that I can create skin for him plus mind that im using a browser based minecraft using java and version 1.5.2

http://www.minecraftskins.com/ welp i get my skins from there