Replying to Video Help

I checked the searchbar and nothing came up, so unfornately I needed to make this theread. I made a little powder edit using GoPro HD footage. It's nothing special basically a song and my favorite runs put together into a 3:45 video. I made it in Adobe Premier Elements 4 (it does what I need done and it's pretty simple) and everything worked out fine, no problem importing the footage and exporting the video. The problem is that the video is nearly a Gb in size. So NS, why is this and how can I resizethe video/fix the problem without really loosing quality so I can upload it to a video hosting site?