Armour is very important piece of equipment, which severely help you during the game. Most armour can be bought from the shops around the world, but the truly great and powerful pieces of armour must be found along the way. The main character of armour is the status changes it gives you, the more powerful the armour the better your stats are. Though, some armour is specifically makes some stats stronger than others. Armour can also have hidden values, like some can block elemental attacks. Remember when you enter a new town; always check out the armour shop. See if the armour they have is better than what you have equipped, and if it is better BUY IT no matter how much it is.
To equip a piece of armour, enter you menu, then go to “Equip”, then go down to “ARM” click on it and in the selection box below it will show you what armour you have. To the left you have a box with the stats, on the left-hand side of the box it has your current stats, and on the right it tells you how you stats change if you change to that selected piece of armour. Just above is the Materia growth and slots it has.