First get a box of tampons that have "lite, regular and super". Both Tampax and Kotex sell them.
Next start with a regular, I find that they cover light days and medium days, unwrap tampon. Notice it's parts, the cottony part called the tampon, inside a tube called the applicator. The tube goes inside you depositing the tampon.
Now insert new unwrapped applicator into your vagina.
Since it'll be your first time stand up with one foot resting on the side of the tub. Now here's the tricky part - you'll want to push it in until it fills like you've hit a wall,the applicator will shorten as you insert it. Once you hit the wall pull out the tube, leaving the cotton tampon in. Stand up. THERE SHOULD BE NO PAIN. If there is then take it out and try again. You'll know you did it right when you've removed the tube and you stand up and there is no pain and you can't feel the tampon. If you are a heavy bleeder,I would check on it every 2-3 hours, only you can tell if you're leaking or not. Now one thing to be aware of, when swimming tuck the string of the tampon into your labia, you'll be less likely to leak.
Using tampons does not take away your virginity.
Good luck and hope you make the team