TheMemeFrog09

I am making a minecraft server for me and my friends but one of them lives across the state and we want to play on a forge server. The only thing i can find is that you should port forward the server but i just don't know how to. I am running on xfinity xfi. Also my sister uses the wifi would it ever affect her and can i set it back to the original port. I don't understand what port forwarding is so sorry if it is confusing. I just cant seem to understand it