It used to be that you would have to modify the user_nicename record in the database directly. This plugin gives a nice UI for people to use.
Modify Author URL
I'm a software engineer/gamer/nerd from Merrimack NH. I solve problems by writing code, and I do believe a well written piece of code can be art. I love watching the New England Patriots on Sundays and action movies whenever I can. If you are reading this and have a great app idea let me know, I'm always looking for a new project.