First you'll need a USB memory stick with CloudReady (i.e. Chromium OS) inside. Follow the steps I took in an earlier blog post. Boot your laptop from the memory stick.
Once you get CloudReady up and running log in with your Gmail account. Click in the down-right corner and choose to setup CloudReady on hard disk. You'll be asked if you are 100 % sure. Yes, you'll want to install CloudReady.
The installation will take ~ 20 minutes. After that your laptop will boot and you can start using CloudReady.
I guess multiboot is not possible?