How do scrolls work in war, how to use them?

You can buy scrolls from the war store and equip them during registration by tapping the little scroll in the top right corner of your garrison panels. Scrolls have different uses, some increase your vizier's health, some let you choose which garrisoned vizier will be attacked first or last, some get more complicated like having a chance at taking attack energy away from your opponents or taking away a % of their overall HP.