Here are some tutorial videos to get you started: Video is no longer available: You can get started using the app pretty easily, all it takes is plugging in the GoPro camera or memory card into your computer and running the software.
A non-linear editor (like Adobe Premiere and Apple Final Cut X) will allow you far more control and the most options, but for those just getting started, or for super quick edits for family or friends, faster and easier can sometimes be the way to go.
The new GoPro App for Desktop works with both PCs and Mac, and is designed to make it incredibly simple to offload, organize, highlight, and quickly edit/upload videos taken with any GoPro camera. Though GoPro has had the Studio app for quite some time, they've just recently introduced an app that is even easier to use.