The second guy is telling the first guy to start officially dating the girl.
When the first guy says he "scored" the girl, I assume he means he hooked up (had sex) with her. Now she wants to see Iron Man 2 and go shooting, which are seen as "cool" things to do in America. The second guy is telling the first guy that he is lucky to have found such a cool girl and that he should get into a committed, monogamous relationship with her.
When people say "lock it down" it means that they have found a great person and should "take them off the market" by dating or marrying that person.