There is no “correct” way to promote CPA offers with Facebook ads.
However, there are more or less effective methods of promoting your offers.
What I would suggest is to set up a lead magnet, whether using an actual “lead generation” campaign or setting up a landing page and using a “conversion” campaign where you optimize for leads.
Your lead magnet is an ethical bribe that you give to prospects in return for their email address. I would recommend having a niche specific lead magnet that is clearly related to what you eventually want to offer.
For example, if you are promoting an offer for the prospect to get a business loan, you might offer an ebook called “How To Finance Your Business Without Using Your Own Money” or something similar, in which you give tons of value (while also making your offer in the lead magnet).
THEN! (Here is where the real money comes in)
You follow up with the prospect over email, nurturing them over time with valuable content, gifts, etc., and sprinkle in offers where appropriate.
I tend to follow the pattern:
Value, Value, Offer, Value, Value, Offer, etc…
Remember, the more value you provide your prospects, the more likely they will listen to and accept your offers!