Username on the forum

[#1]

how can i change my user name on the forum?
please guide me step by step.
Thank you

[#2]

You can't change the username but you can change the display name
Click on Profile on the top menu then Account Related Settings under Modify Profile on the left

[#3]

I'm guessing it's because of a typo 

[#4]

Choose anything you like - the world is your oytser.