How can I add this form on my facebook posts to have clients fill out form?

Also, Can you please advise how can I add this form on my facebook posts to have clients fill out form under each of my facebook posts and not the cover page under contact us, since I already figuered this out.

You may get your form link, and share it in your facebook posts. This way the users will be able to click on the link in order to open and fill out the form.

Related guide:

Where to Find My Form URL?