Essentially there are two ways to use a picture style file (.pf2). The first is to upload it to your camera via the EOS Utility. When you plug your camera into the computer it will likely ask if you want to run the EOS utility, which is where you want to go. Click on the "Camera settings/Remote shooting" link in the EOS Utility.
When the "camera icon" tab is selected you should see a link called "Register User Defined style." Click on that.
A dialog box will pop up that allows you to upload up to three user defined styles. When you select the button with the file folder icon the normal file explorer will come up and you should be able to search for the desired .pf2 file. In this case you can see that I chose a picture style aligned to the DSC Camalign chart. Click on OK and the file will be uploaded to your camera.
The way a picture style is selected with each camera menu and button layout is a little different, but should be obvious to any user advanced enough to be playing with customized picture styles. If nothing else I highly recommend to
The second method only works if you take your pictures in raw format. After uploading the pictures from the camera to your computer you can use the custom picture style in Canon's Digital Photo Professional software. On the tool palette just click on the "Browse" button in the "Picture Style" category. The file explorer will pop up and you can select your custom picture style. I personally think it's better to have the custom picture style in the camera because when I process hundreds of photos from a day of shooting I don't want to have to repetitively do this operation.
This was a good and much needed distraction from my current photo and video work. So feel free to distract me and ask questions if you need more info.