How do I use Steam Coupons?

Question

All those coupons I got from the Gift Pile event are about to become valid, so I might as well ask: How do I actually use them?

Do I sort of activate them from my Inventory, or can I select them at some point during checkout?

Answer 1

According to the Support Article

Steam will apply any of your applicable coupons automatically. Prior to clicking “purchase,” you can choose to save your coupon for later by clicking the “Change/Remove coupon” link for that coupon in your cart.