Armor Equipper is used to equip the armor by just pressing a button. Go through this guide and follow step-by-step instructions to make an Armor Equipper.
The thing you need to do is to dig one block of ground and add one dispenser in it. Place three more dispensers in the same way as shown in the following image.
After this, add a stone button at the bottom of the top dispenser. Use redstone dust on the underground dispenser.
Now you need to add armor in the dispensers. Add a diamond helmet in the top dispenser, then chestplate in the lower one, diamond leggings in the last dispenser and add boots in the underground dispenser.
The next thing you have to do is to change the game mode to survival and press the button to equip armor.