After creating the request in the backend, create an instance of the SCSocialWidget module using Provider: Facebook, Widget: Request, Request ID: the id of the request you've already created. Then set the other two settings (Link Text and Link Image) depending on whether to set the request as a text link or image link. Once you publish the module, you should be able to send the requests on the front-end.
Let me know if you still have issues after creating the module.
-Melissa