SQL Always on question

I am planning to set up Always on with SQL 2012 & windows 2012
server1 & server2 are in datacenter1
server3 will be used as DR which is in datacenter2. 
Those 3 servers are on the same cluster using shared storage.
Here is what I am planning to do:
1. Install SQL in server1 & server2 using IP1 
2. Install SQL in server3 using IP2
3. Set up Alwayson 

Can I add server3 as the third replica inside the availability group? Trying to understand how to add server3 which will be used for DR purposes. 

Thanks!

sqldev