in Windows 7, open the 'Start' menu, type "part" and something called "Partition Manager" or something will come up (it comes with Windows) and it'll show ur partitions that you already have, with the remaining memory labeled as a partition called 'free space'. Create a new partition out of the free space, formatted in EXT4. Install Ubuntu (very easy, the guide will show you how) on the partition and then afterwards Fedora has an option to install over a previous installation of linux (Ubuntu) and thats it.
LifeHacker has a great guide for dual booting Windows 7 and Ubuntu: LifeHacker Guide
since the guide shows you how to install Ubuntu next to Windows 7, and you can choose to install Fedora over Ubuntu, this guide, plus one one extra step is all you need.