How to charge players (via microtransactions) for in-game currency on Facebook?

I’m currently planning a game that I want to release on facebook platform.

I’m looking for a solution when it comes to micro transactions for the special in-game currency. Something like Miniclip’s 8 Ball Pool has to offer… you can buy special in-game credits for real money and they serve a special purpose.

I can’t seem to find anything related to that on forums or on google. Does anyone have any insight on that?

Thank you for your time and help!

FB.Canvas.Pay in the Unity SDK: FB.Canvas.Pay - Unity SDK - Documentation - Meta for Developers

You will need to do all the registration as well: Game Payments - Documentation - Meta for Developers