this is very easy to do. u need to go to your start button and type in cmd it will show you cmd.exe click on that and a black screen will pop up. in the black screen type in ipconfig after you do that all this stuff pops up. scroll up until you see default gateway or something like that. it should say something like default gateway: 192.168.2.1
now go to your internet exporer and type in the default gateway on the search panel.
it should bring up your routers main page, now it might ask you for a password or account or both. if you never used this before the default password is blank so just dont type anything in the password bar. and the default account is admin.
now go to dhcp client list. if you dont see it on the right it might be under lan settings. this tells you who is all connected to your internet at the time. the people you do want connected right down there mac address. then go under firewall and look for mac adress filtering check enable and type in ever mac adress you want to be able to connect to the internet now no one but them computers are able to connect to the internet even if the person has your password