Part 1. Preparation and safety
Objective

Personal safety
Whenever you perform a task in the workshop you must use personal protective clothing and equipment that is appropriate for the task and which conforms to your local safety regulations and policies. Among other items, this may include:
If you are not certain what is appropriate or required, ask your supervisor.
Safety check
Points to note
Part 2: Step-by-step instruction
Install small timing gear
If the timing set on your engine has a smaller gear that does not slide on and seat easily by hand, it needs to be pressed on. Use a brass punch so it won't scar the face of the gear. Tap alternately left and right until you hear a sharp difference in the sound... that means the gear is seated as far as it can go.
Install the timing set while the block is upside down. It is much easier this way for almost any type of engine. Point the smaller gear timing mark straight down.
Install and align large timing gear
Now install the larger upper gear with a bolt to keep the gear from falling off. Spin the gears and line up the two timing marks so that the centerlines of the crank and camshaft are aligned directly through the timing marks.
Install the chain and realign gears
Now pull off the big gear. Slip the big gear into it's chain and hang the chain back up on the small gear so that the marks line up again. For slip-on style timing sets, all three pieces will slide on together at once while the timing marks are lined up.
Install at least one bolt in the upper gear if the set has multiple bolts. Now, double check the timing marks, paint them if they're hard to see, and then tighten the bolt in the gear.
Source: CDX Global