to make something happen. to accomplish something. to "do" something. really anything. to get something done.
imagine if you're flipping through the channels and you land on a moderately decent show. but its not good enough to commit to, so you use the Verizon scroll to see what else is on while watching the decent show in the little box. you notice there's a celtics game on. your buddy, drunky, shouts "Yo, make that be that!" In other words, change the channel.
or... you just get home from work, your buddy calls you and asks when you're gonna be ready to go out. you say after you take a quick shower. he says "Alright hurry up. make dat be dat" Meaning, accomplish the task of showering quickly, so we can hit the bar.
or... you're wasted at the club, you see a hot chick just oozing "im vulnerable, please come fuck me so i feel better about my boyfriend cheating on me with my sister on my birthday." you say, "im gonna get on that" your buddy replies "ya, make dat be dat!!"