You can set it up yourself, or go into an AT&T retail store and have your account set up for the feature. It is a free feature and once you complete the setup steps and create the free Amex Serve card account (a prepaid credit card), it is loaded with $50. The balance is immediately able to be used at many locations, but Amex will also mail you a physical card that can also be used. Through June 30th, payments with Isis will also credit you $1 per transaction, up to an additional $50 per month. Android users need a Secure SIM if one isn't already present (free at AT&T corporate locations). iPhone users need a special case since the phones don't support NFC.
Isis offer details
Offer only available to new American Express Serve Accountholders who successfully sign up for an American Express Serve Account via the Isis Mobile Wallet by March 20, 2014. Offer not available to existing American Express Serve Accountholders or any person that has previously cancelled his or her Account.
Once approved for an American Express Serve Account and if eligible for the offer, American Express Serve will use funds provided by AT&T Mobility to apply a one-time credit to your Account in the amount shown on your Isis Mobile Wallet offer page. This credit will normally be applied promptly after Account approval, but in unusual cases could take up to thirty (30) days following approval. Limit one (1) credit per eligible Account. Subaccounts are not eligible for the Account credit. Offer subject to change or cancellation at any time.