There are many ways to accomplish this. You might as well have a good time at it.
Because you are under age, you won’t likely be buying the things that you need in a sex shop.
You can buy some lubricant at Walmart or a drug store.
You want to buy a zucchini. Pick out a long thick one, ten inches preferably a foot so that you can hold on to it with plenty of length to spare.
First get yourself in the mood by watching some free movies at link
and rub some lubricant on your clitoris and rub it with some good pressure.
When you are good and wet, sit on the edge of your bed with a towel under your bottom.
Coat the zucchini with the lubricant and raise your ass off of the mattress and place the zucchini at the opening of your vagina and the other end of it on the bed.
It’s better to do this quickly and get it over with.
Now drop your ass down on the bed hard and fast. Don’t stop sitting down half way. Keep going until you have the full zucchini buried in your in your twat.
If your hymen is tough and the zucchini stops at it, then raise yourself a couple of inches off of it and come down extra hard two of three times and pop goes the weasel.
The may be some blood but don't worry, you won't bleed to death and the blood will help lubricate.
You may also experience a external vaginal tear. This too is a plus and is why you should make sure you get a thick zucchini. Your vaginal opening will heal in a few days if you tear it and then you can take a big thick cock.
Once you have it in all of the way, lay back on the bed and start thrusting it in and out while rubbing your clit with your hand as fast as light lighting until you have an orgasm.
After you cum, keep the zucchini buried deep in your aching cunt for as long as you can. This will help stretch your vagina so that it can accommodate any size penis that you may encounter.
Do this three to six times a day for a week or so until you can take the zucchini without it hurting.
Most guys will not be up to your zucchini in size but you never know.