Well I had the same problem today, I have bought $30 worth oof AP and to get the payout you can redem it from there website. But heres the catch in order for you to redeem the tier payout you must first waste your $30 worth of AP in-game. If not, you will lose your chance to redeem it by not wasting it in-game for your own purpose.
If you did waste your money in-game for your tier just simply click on this website and press redeem!
This website will just take you directly to the Soldier Front Main page on Aeria to the Tiered Spender sub-section so you can redeem your items.