When is a good age to start teaching discipline, like NO don't play with that ETC.?

My son is 7 1/2 months old. He is crawling and getting into everything. I will tell him NO you can't play with the computer cords and put him next to his toys and distract him and he goes right back to it. Or tapping his hand every time he reaches for something. I don't know if he is old enough to understand that or the emotion or if its too early to expect it???? This is my first child. He is really smart. He already says Mama and Daddy. Among other gibberish. He knows what he is saying, he looks right at us when he is saying it.