To do it properly, you need to set up a timing wheel, I use a cheap protractor from the news agent, costs $1.
Find TDC, accurately, for this you need a dial gauge or do a squish test.
Ideally, next you want to find when your transfer ports are opening, and adjust your base gasket to suit. If your transfer port roof is flat, I usual aim at 123 deg ATC, If they are ramped,120 deg.
Inlet should close around 60 deg ATDC.
Set you engine to desired inlet closing time, and scribe a line on piston, will usually be only 2 or 3mm from bottom of piston skirt.
This will unlikely open the inlet port fully at TDC,
But I believe this is the correct way.