Making armor in Little Alchemy requires combining various elements to create the pieces of armor. To get started, you'll need four basic elements: air, fire, water, and earth. Once you have these elements, you need to combine two together in order to combine them into more advanced elements. For example, combining air and fire creates energy, combining energy and air creates pressure, and combining pressure and fire creates metal.
From here, you can start combining elements to create pieces of armor. For example, metal and air creates mail armor, metal and water creates scale armor, metal and fire creates platemail armor, and metal and earth creates plate armor. You can also combine leather with any of these elements to create leather armor instead.
Finally, you can combine additional elements with each of the above to create various kinds of weapons. For example, combining a sword with fire creates a flaming sword, combining a shield with earth creates a tower shield, and combining a crossbow with metal creates a repeating crossbow.
These are just some of the possibilities, and each creation builds upon the next, allowing you to create more and more advanced pieces of armor as you go. Have fun exploring the different possibilities, and don't forget to combine unlikely elements for an even more creative result!