First, you have to upload a video to YouTube, after uploading the video to YouTube, you have to copy the link of that video. When you copy the link of the uploaded video on YouTube, after copying, you have to enter the forum and click on the Replay or Quote option like other posts by entering the forum. By clicking on any of these two options, you will see three logos showing above like YouTube. Based on the type of video you want to upload or how you want to upload, you choose any icon and by choosing that icon, you paste your link and post it. Hopefully your uploaded video will be visible in the forum.