HOLLISTER.CO-it needs me to put in a p.o box but i dont have one help please?

urgent help please so im shopping online at a store called hollisteco.com and so i put all my info on it and its asking for a p.o box number and i sure dont have one what do i do if i dont put something in the space thingy it wont let me purchase the thing i wanted to buy=[ so someone please help