m1871 rifle sling

[wsfbernie]

I somehow hung onto an original m1871 sling (leather with brass buckle). I now have a decent
rifle (again) but don't know how to install this sling (properly). I suppose the button fastens
at the base (butt end) swivel? Then what? This is not a repro, I've had it for decades.
Thanks for the help! wsfbernie