I need a basic guide on the implementation of Discount Coupons.

I've created a discount coupon through 'Coupon Admin' and Discount Coupon module is installed under Modules->Order Total. That done, i do not see that discount coupon anywhere in my cart.

Can anyone tell me how & where these discount coupons appear in the cart?! Or a link to some thread that already answers these questions. All help is much appreciated. Thank you.