I'm going to start the 5x5 program Monday, how can I add pullups to the program, which day, how many sets and reps, thanks for the help.
5x5 is not 'one' program -- there are many versions, Reg Park's, Bill Starr's, and all of the neo-versions in recent books and websites.
If your version of 5x5 includes overhead pressing, I'd do it on that day. Depending of your experience and strength, you could do 1-2 sets of max reps, or you could do 5x5 weighted chins. If you're a noob, still to the first recomendation.