It's simple!
You have to continue the lyrics of the person above you.
Rules:
Each poster gets one line
Must rhyme with the post line above you
It can be about anything, as long as it rhymes
You can double post as long as you are not answering to yourself (You can't continue the rhyme to your own line, someone must continue your line first)
If there is no way to rhyme the word above, use www.rhymezone.com, or simply start a fresh line.