Hey there,
Well that's a pretty broad question you have there. It's not broad as in I don't understand what your asking, but it's broad as in I don't have much information to go off of.
I guess the most forward and practical answer you'll most likely hear from a lot of people is affiliate marketing. Basically sell other peoples stuff in exchange for a commission on the sale. You can also offer your own goods/services on there.
The third way that I can think of (if you have a very active following) is advertising. Get a trackable link of someone whom pays you to advertise and send them the link and have them pay so much for an amount of clicks.
Like I said some more information like what niche you are in, how many followers you have, how active are they? Would be very helpful in getting more of a precise answer.
Also, why Facebook? Is their a specific reason for choosing Facebook to profit online? If you are just starting out and want ideas ahead of time may I suggest building an email list first with a squeeze page and free advertising methods? That seems to work well for most people and it gives you the ability to automate it later on
Hope this helped
Adam