When you purchase an extra activation for another device with Decipher TextMessage, the activation is immediately applied to your license after your payment is accepted. You can select "My License" in the menu of the software and you'll see the additional activation noted there.
If you don't see it applied to your license, double check that your payment went through and that you did not pay via an echeck with PayPal. in case your transaction is pending and they have a hold on the purchase. You can also contact us via our support page if you need assistance.