There are no hash marks on the baler for you to time it by.
First, turn the flywheel over until the packer forks are 3"+/- from the plunger. Make sure the plunger is on the return stroke, and the packer forks are moving to the right.
On the front lefthand side of the bale chamber is a sprocket driving a chain that runs the knotters and packer forks. You will see five or six bolts that you need to remove. There's a plate, and then a gear within the sprocket which you remove using two of the bolts and the reverse-threaded holes in the gear. Once you have removed that gear, you need to rotate the flywheel until the bottom tip of the plunger knife is laterally flush with the packer forks. Once again, MAKE SURE THE PLUNGER IS ON THE RETURN STROKE AND THE PACKER FORKS ARE MOVING TO THE RIGHT!!
Once that is set, replace the gear, plate and bolts and you should be ready to go.
You don't have to break any chains or anything.