No but I’m still trying new things I can only join the server games and my friend and cousin can join those too but can’t join me directly

Resxt where is it

Hi I’m new to this stuff but I learned how to get mods and download them and play them and then I learned about plutonium and I seen how people play with their friends and the way the did it and when I tried it works in til after you heart the person on plutonium I make the game and he seen me but when he double clicks my name it doesn’t let him join still please can anyone help I really wanna play with my friends