Visit the Alienware Arena website daily. If you are logged in you will receive APR and other 'gifts' from the calender every day. (Displayed on your Avatar details summary if you click on the "View Calender" under " "Daily Reward"). Click on your avatar on the top right corner of the Alienware Arena page, and close to the bottom of your Avatar details summary will be a list of "Daily Quests". Complete those daily, and you will be at level 5 in no time.
For more info, see the following links:
Guide: What is ARP and how can I earn more if it?
ARP Guide Threads
guide on how to get ARP
Leveling Guide for new people