Do this with the engine cold.Remove valve cover. Turn the engine until the lifter is on the base circle of the cam lobe with both valves closed. (No valve movement if you rock the crank back and forth.)
Get a .004 and .005 feeler gage and if the .004 goes in and .005 doesn’t your done. If they both go in you need to tighten up the lash between the rocker and valve tip.
Good Luck and Welcome.