simply reboot your router and it will kick off all the devices attached through DCHP clients [I think your meaning at a guess] -- (its when the router hands out IP addresses to the attached devices.

When you say you put a password on 'just before i even noticed all them ppl' I am assuming that you mean a wireless password (WEP) is this correct ?
I as this because this would mean that these people were connected to a unprotected wifi connection and that is all... rebooting the router with a WEP key enabled (or stronger key such as WPA-PSK) would stop this.

Without being more specific and descriptive I am unable to assist further in all reality.

1) What router do you have - make and model
2) how many systems are hard wired to it
3) who configured the router from new ?
4) is wireless access required, is it protected ?
5) where in the router setting did you see these connected people, what was the information provided