How to use a tampon...help!!?

ok, so i've never used a tampon...and i just recently bought some. I started my period today (not the first time ive had it a few years) and i'm going to lake powell in a month and so i will be on my period while there :/ So two problems: one, please explain how to use a tampon!! and two, i have a very light flow. pads have always been enough, i dont bleed a lot and my period really isnt that bad at all. so i need to use a tampon, but how/when? i dont bleed a lot but i will need to use them because i will be in the water a lot!! please help, i'm really nervous to try. i bought tampax pearl regular, is that the smallest cuz i didnt see any smaller than that! any tips are helpful :)