As the instructional video above, uh, instructs, you'll need to submit your one-liners on the NBA Jam contest page on Facebook. The contest is already underway, and the entry period closes May 19.
Oh, need one to get you started? How about: "Need some fries with that BOOMSHAKE-A-LAKE-A-LAKE?" (Hmm, maybe you should just come up with one of your own.)