Installing with Mac?

[musicman123]

I have a macbook pro running mavericks right now. I downloaded the Express Install 7 iso file and it's currently in my downloads folder. I have a USB drive and a DVD rom I was hoping to put the iso into. I also want to be able to install Amahi into a partition on a seperate external hard drive. Is this possible? Also, can someone please walk me through the installation once you downloaded the ISO? I really have no idea what to do with it... Sorry for the noob question. Hopefully someone can help me!