Adjust the pushrod by hand until zero clearance. This means no up and down movement of the pushrod - by hand. Make sure it is seated on/in the lifter and at the top into the rocker arm. It takes a little practice doing this - as you expand the pushrod, you can get it to move up and down. The more it expands, the less it will move until it is a "zero" clearance. Turn (open) it 2 1/2 turns and tighten the lock nut. What you are doing is depressing the hydraulic lifter to about halfway into its "operating" range. This will allow for expansion (hot) and contraction (cold) of clearances. You will need to do this 2 1/2 turn adjustment with wrenches and be sure to mark the pushrod so you know when you have completed one complete turn (don't recall but it will be 6 or 8 flats).
This is OK but two more things to remember
1. Be 100% sure you are on TDC compression cycle. With the cam cover off this is marks lined up for the rear cylinder, top gear at ~1:00 for front
2. After setting the 2 1/2 turns preload don't worry about the valves opening, yes they do, but after the lifter equalizes (the valve spring pressure from the top overcomes the plunger oil cushion and they bleed off) they are back seated. Whatever you do don't turn the motor over until you can turn both pushrods with your fingers. This is your sign the plunger in the lifter has centered and the valves are back seated.
Orient the holes however you like, it is an annular channel and oil gets to the lifter from all directions.
Side note
Be sure to center the lower rocker boxes and check for retainer to box clearance. This is a 110" issue for sure and many stockers have valvetrain noise because this is not properly set up. After centering the box measure the retainer to box clearance and grind the lower box if need be. There was a running change that fixed this not sure where that occured. You can center the boxes with 1/4" X 20 screws in the center breather holes and copper pipe compression ferrules on the screw or use EVO tapet alignment screws. After you get through that center the rocker supports the same way.