Step 1) Uploading the Video online
If you already know how to do this, or don't need to upload the video, you can skip this step and go to Step 2.
Step 2) Posting it in a Thread / Post
Once you have copied the URL/Link of the video you wish to upload, you will then be ready to post it.
Method 1) Easy and Short
If that is too confusing, or if you think you'll forget, there is another way to do it: