Installing VirtualBox is pretty easy. The most complicated part here is going to be compiling the kernel drivers for your system, but with a little bit of knowledge it will be a breeze!
First, identify the architecture of your system. This guide will assume you are using Fedora 17 on an amd64 archeticture (but the same process would apply for x86).
Second, if you are using a 64 bit architecture, make sure you have VT enabled in your BIOS.
Next, download the latest VBox package from www.virtualbox.org (as of this writing it is VirtualBox-4.1-4.1.20_80170_fedora17-1.x86_64.rpm).
Double-click on the icon for your down to install it. Let Fedora install the package, and half of this will now be done!
Now for the hardest part. First we will install some prerequisites for the software:
sudo yum install make automake gcc g++ kernel-devel kernel-headers
Once finished, we need to actually create the module. You can do so with the following command:
sudo /etc/init.d/vboxdrv setup
When that completes, you should be done! Easy, right?
Test it out by opening VBox and launching/creating a VM!
Just a note, remember that after upgrading your Fedora kernel, you will need to re-create the kernel module again. Just re-run the command for the xboxdrv service and you will be good-to-go.