38mm Won't curl my hair!:(?

I got a new curling tongs yesterday a 38mm Tony and Guy curling tongs. So my hair is long about to my bellybutton but it's fine(thin) I tried using it yesterday but my hair needed a wash so I used it today after a shower and still not much better! The hair is clumping together so it's just a miserable twist of hair:( I'm pretty mad and not many youtubers have tips for this. I hope I haven't wasted my money! Please help me!!!