As someone said the arm of the ruffler should be over the screw for the needle? like when you put on the walking foot. Also make sure it isn't set on zero. Do you have the fabric going thru the right place? We used to play with my moms machine when I was little. She had all kinds of attachments. She didn't even know it was a ruffler. Hers is 70 years old and looks almost exactly the same as mine.
Aslo you could call the store of go in and have them re- demo theirs for you. Good luck.