How do you adjust shift lever Honda shadow spirit 750 so your foot fits?

Check for an adjustment nut on the levers leading to the shifter.

No, the handlebar levers do not lead to the shifter, they lead to the clutch. Using those adjusments will only change the freeplay in the clutch lever, not the shifter itself.

To adjust the shifter peg, you have to remove the lower front left side chrome cover. There is a clip at the top, and an Allen bolt at the bottom. Once you remove that cover, there is a rod about 6" or so long that has adjustment nuts at both ends. Loosen the locking nut at the end closest to the peg and adjust the height with the other nut. A little turn makes a pretty big difference. Once you have it where you want it, be sure to tighten the locknut again. Replace the cover and you're done.