IRecently Got My 1917 Artillery and How Do You Set The Range?

[cirelaw]

I own an '08' Navy and 1920 9mm Luger Carbine.I want to take my first shot with this way cool artillery, How do I use this range thing? What do the numbers mean?? Just delived is a dated ang Germany stamped duel leather mag pouch. Now between a snail drum and loader another $3-$5k This is becoming more than alimony!