How to play D&D with a Starter Set?

My friends and I have been wanting to try out D&D and I want to learn how so I can play with my gf, (She plays with her friends) but I want it to be a surprise so I don't want to ask her. So I cracked open the set to find a large DM guide and a basic starter guide already using terms I don't know. If any one could give me the basics or maybe an online guide for a fast start that would be much thanked.