Follow these steps to upload your video:

1- Go to youtube.com and create an account or login with existing.
2- Once logged in go to upload.youtube.com/my_videos_upload and upload your video. The trick here is if your video is HD or just a big file then you can compress before you upload.

The best and easiest way to compress it is using this free software Any Video Converter

My suggestion is that if your video is over 200mb then you are better off compressing before upload.

3- After you have successfully uploaded your video you can then go to www.youtube.com/editor and edit your video. You can do basic editing here like trip parts of your video and also add music.

4- Once your video is ready you can get its link and just paste the link into your new thread and it will automatically embed the youtube video in the thread ready to be played.

Dimitri