Although this functionality has been available for quite some time, many still do not take advantage of it.
Setting up usernames for your personal or business Facebook pages is a very simple process. It is also very convenient; if you want to direct someone to your Facebook business page, for example, the URL would be as simple as facebook.com/Connexins (instead of the long and convoluted default URL).
Although you can set up the username for your personal profile any time, Facebook pages (for a business or an organization) need at least 25 people to “Like” the page first before you’re able to set up a username for that page.
Login to Facebook, and visit http://facebook.com/username. Follow the instructions to set up the username for all your Facebook pages. Please note that usernames are final, i.e. once set up you cannot change them!