-First of all you will need Skin Edit. Download it here.

-Go to the Start menu and search for %appdata%, you gonna see a folder called Roaming. Click on that folder, then .minecraft

-After that click on Bin, and open minecraft.jar with WinRAR or 7-zip, and extract the folder armor to the place you want

-After extract the folder open Skin Edit (You will need the newest version of Java to open it)

-When its open, click on File and then on Load (Ctrl+O) and go to the armor folder you extracted from minecraft.jar and select what kind of armor you will use (Diamond, Gold, Chain, Iron, Leather), in this Tutorial I will use Diamond

-The First file of every armor are the Helmet, Chestplate and the Boots, the Second file is the Leggings

-Put the colours you want on your armor and remember to use the Dodge and Burn tool to make your skin more realistic

-After making this steps save it by going to File and click on Save (if you want to save in the armor folder) or Save As (if you want to save it in another place)

-Now if you want to put in a texture pack, put the armor folder with another stuff of your texture pack, if you want to put it on minecraft.jar, just open it with WinRAR and paste the new armor folder