In your park distribution there's./ec2/
folder, where you can execute:
./spark-ec2 -k spark -i ~/.ssh/spark.pem -s 1 --region=us-east-1 launch spark-test
This will launch an cluster with a master node and one slave.
./spark-ec2 -i ~/.ssh/spark.pem login spark-test
You can download the key spark.pem on the ec2 console.