Cut to the same number of links as the old chain, not counting the master on either. You should have an inner link at each end once cut. You can always check by wrapping the chain around the chainwheel and installed wheel with the wheel roughly centered in the dropout slot before cutting. You should have roughly one link space between the two inner plates.

Once cut, install the chain on the bike and snap the master link on. Pull back on the wheel so that it is cantered in the frame with only very slight tension on the chain. Tighten the right nut snug but not all the way tight. Recenter the wheel and tighten the left nut slightly. If a coaster brake, attach the brake arm with the clamp on the stay loose to allow movement. Turn the cranks to find any tight places in the rotation. Always rotate the cranks forward during this process - use your hands rather than back-pedal to stop the wheel.

Place at the cranks at the tightest point and loosen the right nut just enough to release chain tension. Recenter the wheel with the left nut and crank around again. Fine tune till satisfied, tighten brake arm clamp.