It's not as seamless as it could be, but still quite workable.
Using a PC
1) Right click on the image on YouTube. You'll get a popup menu over the video.
2) Click "Copy video URL"
3) Click the youtube button above your text box.
4) Paste (i.e. Ctrl-V) the URL between the tags. (The cursor should already be sitting between them)
1 post • Page 1 of 1