The amount of your active duty military pay is the amount from the W2 box 1 for your military pay.
Typically, when you enter the form W2 information in the Federal "Wages and Income" section, you will arrive at a page titled "Uncommon Situations". There you need to select the box for "Active Duty Military." This will tag that W2 as military when transferred to your state tax interview. In most state interviews you may only need to verify the amount.