Contacting multiple machines over ssh

This is very fundamental, so please excuse me.

I am new to linode. I was under the understanding that I could run multiple machines under my linode, so I could perhaps run a web server and a mail server. I am thinking that I misunderstood that completely.

I have two images, and two profiles, but I can't figure out how to run them both at the same time. I only see one IP address, so can't see how I would ssh to multiple machines either.

Thanks in advance for clarification.