About 5-6 years ago the way to embed YT videos was different and it has changed and might even change again who knows.
Very Important: Please don't use this to post a YT video anywhere besides your personal profile. (you'll have a bad time)
Step 1: Locate the song you want on YT.
Step 2: Press the share option below the video.
Step 3: Press the "embed" option and copy the text like so.
Step 4: In the "edit your profile" section of your profile paste the embed you copied.
Step 5: In that embed you need to find the end of the "URL" of the YT link
Step 6: At the END of the main URL type ?autoplay=1
like so.
Step 7: take a bong rip and relax B^)