Sure I do. Let me go from the start. xD
First you need part of the video url.. for example:
http://www.youtube.com/watch?v=2X9w_FQLYmM
From that.. you'd take last part '2X9w_FQLYmM'
Change it to 'v/2X9w_FQLYmM' and copy it.
Then go to your Profile Details, and scroll down to where it says YouTube Video URL, and paste it in there.
Lastly, the option right below that one, says 'Swap Video', select Yes, and that'll swap the video with your profile picture. (b ' ')b Hope I explained it okay.