Fit the timing light pickup to the HT lead to Cylinder #1 - on a modern timing light it might be an inductive pickup that just clips to the HT lead, otherwise you'll need to pull the lead and fit the pickup to the 'plug, and replace the HT lead to the pickup. Hope that bit makes sense.
Next connect your timing light to a power source, mine fits to the vehicle battery, and start the car making sure all the cables and timing light won't foul on the fan.
Aim the timing light at the timing marks (on the front pulley and crankcase) and pull the trigger. You will get a flash of light every time Cylionder #1 fires, giving the effect of freezing the timing mark on the pulley so you can see if it lines up. A blob of white paint in the marks might make them easier to see.
If everything is as the manual says, pack up and slap yourself on the back, if not, slacken the bolt holding the distributor in place (stop the engine first, or you'll get chopped to bits by the fan). Re-start the engine and gently turn the distributor until the marks line up (or are where you want the BTDC to be).
Stop the engine, tighten up the distributor, pack up an go enjoy.
Oh yeah - on some models you should remove the vacuum advance and plug up the hose while adjusting - depends on the figures quoted in the manual, it should state mechanical advance only or something like that.