How do i upload an css :S

fnon

this is kinda important, because i've got the css from a site with firebug, and i eddited it so it would look cool, now i want to upload it so people can use it through stylish on this website, but i have no idea how :S
plzzzz help me, i really can't solve this thing!!!
need ur help A.S.A.P!!

greetings fnon

JasonBarnabe

Go here.