Hey! Great to hear and thank you!
Anyone can use any kind of armor, but the Ref is invited to create reasons why it may not make sense to, or restrict it.
Shields and helmets typically just break or bend if hit, but they block all damage from that attack.
Armor has three kinds mechanically
Light
Medium
Heavy
You can use these to reroll a defence roll 1, 2, or 3 times, respectively. If you succeed at the reroll, your armor take the damage instead of you. This has to be repaired or recharged back in town.
For me personally I let magic users or sneaky wear heavy armor, but I come up with reasons they shouldn't or flavor them to be magical and more expensive to recharge.
Hope that helps.