Posting a YouTube video is relatively simple. Most sites require the entire shared address. For instance the entire address for Fables Forge promotional video is: https://*youtu.be/iAD2l_IhRE0.
However, if that was entered into the link box when you click the video button in the top right corner. You would get nothing. Instead, all that needs to be entered is the video code: iAD2l_IhRE0. When doing this, you will see the results below.
You do not need to change any of the parameters, except where the video originates and its code.
Note: you can also just post the entire url inside this box and it will also work.