Questions about: nomodeset

I know that editing the boot options line and adding 'nomodeset' solves my laptops problem during LiveCD mode, what I don't know is how to set it at boot up through Grub2 after I've installed Ubuntu. So, my question is, how do I set nomodeset before
I have a Panasonic CF-52 Toughbook with an ATI Radeon HD 5650 graphics accelerator. I recently had some troubles installing both Ubuntu 12. 04 and Mint 13, as described here: http://forums