Salesforce has made great strides in Winter'15 addressing a major pain point in setting up Salesforce 1. The issue was you had to navigate to many places in the set up menu to get this done. The Winter '15 release brings with it a simple wizard style set up that will get you up and running in no time!
Here are the Steps:
A great add on to this is the Chrome Extension that allows you to view ANY Salesforce page as it would look in Salesforce1!