The general method is this:
You remove the fuel injector line going to #1 cylinder.
Put the throttle in full fuel position. MAke sure fuel cut/shutoff is open (fuel can flow).
Rotate the engine by hand until fuel is just seen at the top of the injection pump for cyl #1.
Then look at the timing marks on the flywheel. It should be at 26 BTDC for your engine.
If it is wrong, the adjustment is made with shims between pump body and engine.