With distraction. Show him another object that he will find more interesting so he forgets about the first one. Better though: remove all the objects to begin with that he is not supposed to touch before he discovers them.
You say NO very firmly ,no yelling simply remove it with a NO his crying is okay, let him cry, do not feed into it. , he will stop ,you can also use the distraction method and get him interested in something else or some other toy or game, music, dancing, he will immediatly enjoy what you are distracting him with....