We're here to help
You mentioned that you setup the Facebook app and think it works. The easiest way to test and know the app is setup is to login on the front end of your site with your Facebook credentials. If you can do that, and a user is created (or linked to an existing Joomla user), you know your Facebook app works. Logging in on the front-end is also required to setup a channel. You can only select from users that have connected their Facebook account to your site.. so if you're not seeing any users, I'm assuming you just haven't logged in on the front end.
The general flow for setting up a channel is:
* Login on the front end with a Facebook user
* Setup the channel for that user
* Login again on the front end with that user. This is for JFBConnect to request additional permissions from the user necessary to read/post to Pages they are an admin of.
* Finish setting up the channel for auto posting or showing a stream on the front-end of your site.
Please note, after you setup the channel, you can disable the SCLogin module and social logins. Even if you're not interested in the social login ability for your general users, it needs to be setup, temporarily, to get the proper permissions for the channel to work.
I hope that helps, but should you need anything else, just let us know!
Thanks,
Alex