Hi there and welcome
For which service on the phone do you want the username for (what are you trying to do that requires a username)? As when you initially set up the phone it has you create one.
The manual you can get from my link below
Click me to open
If you have any problems, or would like any additional information or assistance, please do not hesitate to let me know.
And if you can take a second to rate my service by clicking one of the stars at the top of the screen then submit, that would be greatly appreciated.