Go to your Facebook profile. Once you're there, click the videos tab next to Wall, info, photos, etc.
When the page loads up after you click it, click upload on the top right next to where it says "Record". It will make all your files pop up and select the video file you want to upload. It will upload automatically after that and will take a few minutes to process.
If the Videos tab is not there, click the plus sign tab (+) on the right of all of them and select the videos tab or search the videos tab on the bottom of the menu box.