How to store sessions in DynamoDB using Rails 3

We are using rails 3.2.x, I want to store our session in DynamoDB. I tried the 'aws-sessionstore-dynamodb' gem but I don't know where to specify the credentials. We use PostgreSQL in our database.yml so I don't think that I'll have to specify it there. Any thoughts?

I already ran the generate command below but I still can't figure out where to put the AWS Credentials and the endpoint of the DynamoDB.

rails generate sessionstore:dynamodb

This is the github page of the gem I'm trying to use. http://ift.tt/1P5smRG

If you are storing your sessions in DynamoDB using another gem, I'm also open to that.