What if you cant get your penis into the vagina?

Purchase some sexual lubricant -- for best use with a condom, go with a water-based lubricant. Other lubes may damage the condom and increase the risk of pregnancy or spread of any diseases either of you may have. If that still doesn't work, try more foreplay to get her more 'in the mood' and get her body more ready to accept. Actually, that should probably be the first thing you try. =) And always make sure that she is comfortable with what's going on, or you're not going to get very far.