To see what you can spend your miles on please log into the Fleet Feet app. Click on the present icon with the word "Rewards" below it, which is located in the bottom middle of the app. Then click on the "Available" section.
Here you will see items you can spend your miles on, as well as sweepstakes you can spend miles on to enter. To purchase an item, simply click on an item you would like to purchase, and press the orange "Redeem" button. This will take away the correct amount of miles, and send you a coupon for the item you would like.
Finally head to your local Fleet Feet store, show them your coupon on the Fleet Feet app (you can find it in the same spot as your $15 rewards coupons), and they will get the correct item for you.
Note: Fleetfeet.com cannot ship out items that are purchased with your points, this can only be accomplished at your local Fleet Feet store.