In reply to Phil1919:
Going back in time a bit, and assuming 3 speed Sturmey Archer
Put the bike into second. Move the pedals back and forth so that you can feel the drive being taken up, and slowly move the gear lever/twist grip from 2nd to 3rd (note - it's some time since I last did this - it may be third into second - go whichever way is tightening the cable). You can move the pedals by hand, but it's easier freewheeling gently somewhere where your total lack of concentration on your surroundings won't get you killed. At some point, the gears will slip. You need to adjust the wee chain so that that slipping point is mid way between 2nd and 3rd. Make sure that you use the little lock-nut to hold it in place when you're done. When you think you goit it right, check it again as above. 1st and 2nd will be fine if 2nd and 3rd are right.