Tampons

So I have to take swim classes next year for the whole school year and I’m trying to start using tampons so I wouldn’t have to miss classes and then have to make them all up later. I tried using a tampon when I had my last period but it didn’t work out because it was towards the end of my period and I also chickened out. I’m really scared to try again because my period is coming in 4 days but I really want to get this over with. Any advice on how to stop freaking out over this? I’m honestly so scared but I’m not even sure why!