What a great question! Monetize your social media presence!
The following should be sufficient to get you through the process. Caveat/Friendly Warning: you can only add online ordering to a Facebook page that you own or have admin access to. (see attached screenshot and/or navigate to "Advanced Settings" > "Facebook app" to follow these steps)Step 1: Choose your menu style (regular or picture heavy).
Give it a shot, and feel free to reach out if you have any further questions.