Need to ask why your trying to adjust it?
Usually the timing is set and doesn't need adjusting.
But if you need to??
At the top of the towershaft there is a plastic connector.
It has a 3/8(??) nut on a rod that has a slot for a screwdriver.
You undo the nut and turn in/out for desired setting.
Some motors need the throttle pushed all the way forward to access the nut.
Read the first 3 posts in this forum.
It has a bunch of posts by contributors that give steps on doing various procedures.
You should pay attention to the one by FrankA called a Linc and Sync.
Covers timing and linkage setup.