When you set up a Facebook page you are allocated a URLbased on the page name you select and a rather long random number - it will be something like https://facebook.com/Your-Business-Name-179613278722454.
To tidy this up, look more professional and make it easier to share you need to claim your own unique page URL such as http://www.facebook.com/Truska.
To do this yu must have at least 25 likes
then
From the Facebook Page:
Select About
Page Info
the Edit the Username
If the one you want is available click create Username
Note you can only change this name once so make sure you get it right first time. If your chosen one is already gone take you time time to work out the best alternative..
More can be fond at https://www.facebook.com/help/203523569682738
Here are some guideline on choosing your Username as well: https://www.facebook.com/help/105399436216001