I will attempt to explain the installation for you as simply as I can with words.

The three position crank sprocket should have the markings of a triangle, a circle, and a rectangle all next to a separate keyway. The standard position would be to install the sprocket on the crank with the "Circle" in the 12 o'clock position when looking from the front of the engine. The crank key will be located at about the 2 o'clock position. The cam sprocket is then installed with the "dot" located in the 6 o'clock position. The locating pin on the cam will be at about 3 o'clock. Now rotate the asssembly (timing chain installed on the sprockets) until the cam sprocket "dot" is at the 12 o'clock position and the crank sprocket "Circle" is also at the 12 o'clock position. The #1 piston is now at TDC on the firing stroke and this is where the distributor can now be installed. Both rockers for the #1 cylinder will be slightly loose and both valves will be closed.

If you install the distributor with the crank "Circle" in the 12 o'clock position and the cam "dot" in the 6 o'clock position this would be for the #6 cylinder to be at TDC on the firing stroke.

Be sure that the three position crank sprocket is installed with the crank in the correct location. Crank key at 2 o'clock (#1 piston at TDC) or the cam will be 120 degrees out and you will bend pushrods and will not get the engine to fire. I've seen this happen before when the three position crank sprocket was installed incorrectly.