I don't have a KitchenAid attachment, but I've owned an Atlas-Marcato (Italian) one for years and love it.
My only recommendation is to go slow. Don't rush the dough and begin at the lowest setting and run the dough through each level several times, folding the dough over itself on the passes.
The best thing to do is to experiment. You'll get the hang of it and discover how it works.
Have fun. Homemade pasta is soooo good. Wait until you make your own spinach pasta. Yum!