If you would like to change your Tapni username please follow below steps:
Step 1: Click on the menu (upper left corner)
Step 2: Click on “Settings”
Step 3: Click on “Change username”
Step 4: Enter your new username
Step 5: Click on “Update username”
Each username is unique to one person. It happens that the username that you are trying to enter is already taken. Try another one and it should work.