Once there you will see a drop down box where you can select your page you want the custom url for.
If your page does not have more than 25 people that have liked it when you select it you will get a message like this:
Your Page Name is not eligible for a username at this time. In the future, Your Page Name will be able to set a username.
That is all Facebook will tell you. Now how do you pick that name? Well for us we entered our keyword phrase we want to rank for, Las Vegas Web Design, so our fan page is http://www.facebook.com/LasVegasWebDesign. So when you search Facebook we come up towards the top. So you should do the same thing, pick a keyword phrase that your Las Vegas business targets, for better results when someone searches.
***Important note, be 100% on your choice for your Custom Facebook URL because once you pick it, you are stuck!!! In order to get something new you would have to delete your Fan Page, get 25 people to Like it then request another url...what a hassle, so be sure what you choose is what you want.
So that is all you need to know about creating a custom Facebook URL, it is really that easy.
If you want to see an example of this visit us on Facebook http://www.facebook.com/LasVegasWebDesign