From the Inbox page, tap the button "X Credits" button in the top left corner where X shows how many credits you have left.
From the left bar Menu, tap "Earn Free Credit"
1 You can earn free credits by watching a video or watching a premium video
2 You can earn free credits by completing offers which includes downloading apps, signing up for web services or completing surveys
3 - You can buy credits packs
4 - You can earn credits by inviting friends
Remember, you don't need "credits" to call or text TextMe users, so invite your friends to TextMe!
Enjoy TextMe Apps!