Upload your video to PinkBike, above the typing box when your typing a post, the line with the smilies on it, click the little icon that is 4th from the right, copy and paste the adress from your uploaded video into it. Hope that made sense.
Yes, to expand a bit on it. Pinkbike supports the 3 major "free" video hosting sites. 1st beeing pinkbike.com, we feel that we beeing the forum used should get first and foremost chance to get it on us, 2nd beeing youtube, and 3rd beeing google video.