I'll lay out some basics for you...
1) Make sure your hands and penis are cleaned. Trim and file your nails and then wash them. Typically I'll wash my hands and then jump in the shower to clean my dick.
2) Finger her if she's willing and into it. If your penis is average sized then as long as both your index finger and your middle finger can comfortably fit, most likely so will your dick. Fingering her will also tell you if she's into insertion. There are plenty of female canines that do like to have their clits played with, but are uncomfortable with having anything inserted into their vagina. If she looks uncomfortable, of course, stop immediately. If she is into it, great! Don't be afraid to bring her to an orgasm before actually making love to her.
3) I recommend using lube over saliva. Normally the brand I use is the Astroglide branded Gel lube. You'll want to make sure the first ingredient is water.
4) The vagina is usually 1 inch (2.5 cm) higher than the entrance of the vulva. You'll need to either insert your penis at a 45 degree angle, or you'll want to insert your penis into her vulva, push up, and then push in.
5) Seeing that you've mentioned she is a virgin, be prepared to feel a choke point a few inches (7-8 cm) into her vagina. If it feels like you're hitting a wall DO NOT try to force your way through. This will cause her a lot of pain. For some canines this choke point is very tight, for other canines this choke point is almost nonexistent.
6) If you do manage to have sex with her make sure you take her outside to pee 10-30 after the whole ordeal is over. Also, don't have sex with her just after she's peed as well. Normally, I'll wait 2.5 hours after the last time my girl has used the bathroom before I make love to her. Failing to do this will increase the chances of her getting a UTI.
7) Hope for success but prepare for failure. Not everyone's first time will be a success story. If at any point she looks uncomfortable, stop and disengage immediately. Pet her and let her know she's done nothing wrong.