How Do You change Your User Name Page on Facebook?

To find the usernames of your pages on facebook  and to change the usernames please Follow these 3 steps  :

Step 1

Log into facebook.com.

Step 2

Select Account Settings under Account in the upper right corner.

Step 3

Click "change" next to Username. Enter your new user name in the box and click Check Availability. You cannot choose a user name that someone else is already using.

or the easiest way is click in this link https://www.facebook.com/username
 

A window will open directly contains all usernames of your pages .