Remove the #1 spark plug. Place a rolled up plug made from paper tower in the plug hole. Remove wire from the ignition coil to the distributor so the engine does not start. Bump the starter to bring the #1 cylinder up on the compression stroke. On the compression stroke the paper plug will blow out. Now feel in the plug hole using a screw driver or other tool to feel the piston top. Rotate the engine manually and feel when the piston is at the upper point of the stroke. Then see where the timing mark on the harmonic balancer is pointing. It should be real close to Zero.
Some additional info can be found online. Here’s a youtube explanation:
https://youtu.be/8Fj4lgt_WyQRon
