You can create a pen name through this link: http://www.writerbabu.com/pen_names.php . You can also reach this page through a provided link on your profile page or through the link in the navigation panel that slides down by clicking on the horizontal stripped symbol in header. So once you are on this page you just have to enter the pen name of your choice and click on the "Create Pen Name" button, and that is it. Your pen name has been created and you will be taken to the profile page of you new pen name.
To revert back to the original profile, you just need to come back to this page through the link on profile page or the link in the navigation panel and click on the link named "Click here to revert back to original profile". And you will be reincarnated into your original profile.
When in your original profile, go to the pen profile page and if you have already created your pen profile, you can see your pen name there. Just click on the pen name to switch into your pen profile.
As of now, you can have only one pen name.