The best starting point is the Park Tool website.
For a quick summary:
Disconnect the rear mech, set up the end stops (high and low limit screws)
Screw the mech cable adjuster in fully, back it out one turn.
Put the shifters into top, pulling the cable taut and clamp the cable.
Shift down one gear - turn the adjuster a quarter of a turn increments until it shifts cleanly onto the next cog.
Usually a little more finicking with the adjuster on the other gears and you are done.
Ride it or milk it!