How do i put a pword on my computer so know one can just hack in?

I have just installed the belkin g wireless router,so that my daughter can have the intrenet on her laptop,well whn i was setting it up,i missed out the part were you could put a pword on,i thought i would do that once i got it installed,well after doing so i have went back to putting the pwrod,but it takes me right through the installation process,and am abit unsure of doing this as it might muck anything up?,how do i put the pword on?,oh i have the internet on a desktop and also going through to the laptop...thanks