Add 2 counters to your Resource. Play only during your build step.
Put 1 build counter on a partially built card in your build zone. Play only when the Ground battle step starts.
Keywords
Armor
Armor: An isolated, static ability that means, "This unit can only be hit on a roll of 5 or more." Armor works against dice of damage and attack dice. It redefines what die roll is required to hit a unit. It doesn’t modify the die roll like Accuracy. A unit with Accuracy 1 attacking a unit with Armor hits with 4's, 5's, and 6's.