Well myTube has a web page you can set as a favorite. You open the YouTube video in IE of what you want to watch in the app. Then open the app favorite, it will direct the video and open it in the app.
Other way is to hit share in the app bar and share it to the myTube! App (though you'll have to back out and open the app afterwards because sharing simply saves it to "view later"
(Apparently the web page for direct access isn't directly available from the app anymore. I can however confirm it still works and I have the link readily available (( javascript: location.href = "mytube:link=" + location.href; )) and save that as a favorite.)
You click on the three dots, then share page, and mytube should be listed there, click it and it should open the app with the video that was in the page. Sorry for my English.