Armor is a piece of equipment like any other. If it makes sense your character should have it, you might simply mark it down on your character sheet. However, some GMs might want to see that your character has the Resources to afford it. If you want medium or heavy armor, ask the GM if they agree it makes sense for your character to have it.
Armor is described with aspects. You might describe your armor with a great deal of fantastical/artistic license, but when it comes down to it, you should assume it fits under one of the following categories. Selecting armor does not require you to devote an aspect slot to describing, unless you wish to purchase a special masterwork or magical set of armor with extras.
When you wish to have the benefit of armor, you invoke it. Light armor can be invoked once per session for free, medium armor can be invoked twice for free, and heavy armor can be invoked three times per session for free. After that, the armor isn’t destroyed; you can spend a fate point to continue to invoke it for defense. Also, when you have time and assuming you have tools, you can use Crafts to make “repairs” on your armor in order to regain one or two free invokes.
This type of armor includes padded armor and leather armor types. As long as you are wearing it, you can invoke it once for free per session. A GM can compel it against you when you try to hide the armor, are soaked, or if heat could be a problem.
This type of armor includes mail armor, ring armor, scale armor and lamellar armor. Because it’s denser and heavier than light armor, the GM may compel this aspect for any of the reasons under light armor, as well as when stealth is important, you try to swim in it, or if you attempt a long run in it.
Plate armor is the ultimate expression of this kind of armor. Although it provides impressive protection, the GM can compel it in any situation that might apply to medium armor, as well as whenever standing out might inhibit the character, or when you might need to move quickly.
Shields are a very hand type of armor that is quite versatile. A shield provides an aspect that can be invoked for free once every scene. The GM can compel the aspect should you need both hands, or if you need to do something with your off hand.
Copyright Notice: Rules on this page are brought to us by Chapter Three of the Fate Freeport Companion, released under the Open Game License. The rules above are paraphrased, but the idea comes from the aforementioned book.