Fairly simple. You post a confession, and the next person gives you a dare based on your confession (and then posts their own confession)
EX:
Person 1, "16/F I lied to my mom this morning. She asked if she looked pretty and I said yes."
Person 2, "bad girl! spank yourself for every time you lie for the next month"
(Or something like that)
My confession: I borrowed my little sisters underwear and dress for a crossdressing dare, and then i put them back in her drawer with the clean clothes