Glad that you are headed to an Appleseed! The basics of slinging up with an AR are the same as what is shown at the link above. As far as connecting a sling to your AR, for a GI-style sling you will need to have 1-1/4" swivels installed. How they are installed depends on your rifle's set up.
The most common rigs I see on Appleseed lines for a front swivel are either A2 style or a rail-mounted swivel on the bottom rail of the handguard or gas block. I would avoid rigging your rifle with a sling on the side rail of the handguard or gas block as this provides less stability as it pulls the rifle to the side.
If the stock that you have has a means of attaching a rear swivel, use that, and you are all set. If not you will have to determine if you want to mess with trying to rig a rear swivel. The most stable of the sling options taught at Appleseed, the loop sling, is the most popular and only requires a front swivel. However, if you wanted to use a hasty sling you would need to rig a solid rear swivel as well. For the kinds of shooting done at Appleseed, a loop sling works very well, for most folks.
Last edited by rconnerley; 09-19-2012 at 12:19 PM..