I used one in the 1960's. Jack up car, support under frame. Place magnetic pickup under lower control arm at ball joint. Place a chalk mark on the tire. Spin the wheel and watch balance meter for how much weight is needed and note where the chalk mark is positioned while illuminated by the strobe. Then stop spinning the wheel, turn wheel so chalk mark is where the strobe illuminated it. At 12 o'clock is the light point needing weight. If more than 2oz. split the weight into 2 and place one inside wheel and one outside wheel at the 12 o'clock position for dynamic balance. Sorry if this is a little terse, I'm getting old. You can also place the magnetic pickup against the brake backing plate to check dynamic balance. For rear wheels jack up and spin but keep the rpms down to no more than 45 mph on the speedo.
Roy