To enable username swapping
you need to go to the User CP
and click the Edit Settings
button, then check the box Enable Account Swapping?
This feature allows you to swap between your Usernames in one click. Make sure that any names you want to swap between have the same email and password. When you have the enable swapping box checked for every name you want to use this way you will see at the top where it says Welcome ,
there will be a dropdown box that you can choose the user name you wish to use. From then on you can select your user names from that box to switch which name you want to use.
You should see something like this: