You can download Fedora from this link http://fedoraproject.org/
Burn the ISO to a CD or DVD using a CD/DVD burning software such as Roxio, Nero or ImgBurn
Put that CD or DVD in your computer and re boot so the computer will boot from there and select install.
The installer will ask you if you want to install along side Vista or if you want to format the hard drive and install only Fedora to it.
up from that point all the decisions are up to you.
Good luck to you!