The ones most often used are to successfully score with a girl via some line or to get drugs.
In this version, it means to generally do good. If someone needs to get something done fast, they need to Pick Up, or if they say they're going to talk to someone they fancy and that person comes along then they need to Pick Up. More or less it means to just get something done.
Guy #2: She's right there, pick up.
Girl #1: I only have one more day until this assignment is due in and it isn't done yet!
Girl #2: Pick up!
"COME ON, PICK UP!"
No, man, I was there till the lights went on.