After the EC2 instance is started, you can access the Bayesian Workbench RStudio Server with its public IP address. For example, if the IP address is 10.11.12.13, typing http://10.11.12.13 in the browser will bring you to the following startup page:
The default username is ruser and the password is the EC2 instance ID that has the form of i-0c7fadc4dc193eca7.