Go to your Settings icon. Usually, this will look like a gear (see below).

Once you open your settings, click on "Apps."

You should now see an alphabetical list of all the apps installed on your phone. Scroll down until you see "Cardtapp."

Click on "Cardtapp," then click on "Storage."

Click on "CLEAR DATA."

Click "Delete."

Close your settings and return to your phone's home screen.