Arena Points are acquired at the end of the week during maintance and are based on your Team Rating.
In order to gain points, you need to have the following:
Points are NOT summated from bracket to bracket (i.e., if you're in three active arena teams--one for each division--your points are only taken from the team that would earn the most points).
The Arena points 'cap' is set at 5,000.
The formula to determine points for a 5v5 team is the following:
If X>1500: Y = 1511.26/(1+1639.28*Power(2.71828, -0.00412*X)) Else: Y = 0.22*X+14
They are several point calculators on the internet, including Blizzard's.