Click on the purple icon at the bottom, it will open up a box that has 4 tabs.

Information: This shows the total stats your battle armor is giving to each of your ninjas.

Upgrade: Here you spend cloth you get from Strong Approaching to increase the stats of your armor

Improve: Here you spend thread that you get from Strong Approaching to increase the stats of your armor.

Transform: Here you just chose which look you like most.