You can't use Palace to upload a video to youtube because youtube does not accept feeds from external programs. What you can do however, is upload a video to youtube and add the youtube link into Palace.
Then, when you upload available properties, the youtube link will also get send through to the receiving site. That site can then use the youtube link to embed the video in the website.
Trademe doesn't display youtube links, but your own website can be amended to show this.