
Setting this up is easy. Just go to the Promotion and Facebook sub-tab. Enter your Facebook Page and click Add. Note that you will need to be a Facebook Admin for that Page to make this work.
Here are the two steps. First enter your Facebook Page address.
Then select the Facebook Page you manage. And of course hit Save once you have done this!
The one thing we are waiting on Facebook for is the make this work from the Facebook Mobile App. RunSignUp would work wonderfully with our mobile ready registration, but most Facebook Apps are not mobile ready so Facebook auto-hides this on mobile phones. Hopefully this will change at some point!