You can buy sling mounts that attach to the magazine tube for the front attachment point. Most people use that kind of mount on tactical/defense shotguns. For the reay you can either screw in a mount to the stock, or go with a strap that wraps arount the stock.
On my Stoeger 2000 defense shotgun I use a mag tube mount and a web wrap around the rear stock with a 3 point sling. Works well for me.