>>1400466work out a way to suspend it so you can pedal and shift at the same time and tune it. Either a ghetto bike stand or ropes to hang it
unclamp the cable
eyeball that the derailer hanger is straight
move the derailer with your hand, and adjust the high limit and the low limit screws (next to each other) so that it bumps up in the right place at either end of its travel (your low limit is not set correctly).
Then shift to the smallest cog on your shifter, and clamp the cable.
fine tune indexing with the barrel adjuster.
Shifting to larger sprockets is accomplished by tightening the cable;
if such shifts are slow, the cable is not tight enough--
turn the barrel counterclockwise to tighten it.
Shifting to smaller sprockets is accomplished by loosening the cable;
if such shifts are too slow, the cable is not loose enough--
turn the barrel clockwise to loosen it.
https://www.sheldonbrown.com/derailer-adjustment.html 
