MY SMC Rogers router kept disconnecting simultaneously, we got people to come in and look at it and they "fixed" it but the problem continues to happen. We connected a Linksys Router to the SMC and now wireless works perfectly. The problem I have now is there are atleast 5 other people using the connection. I cannot get anyone from Rogers to help for some reason. And putting a password on the linksys router seems impossible (we have a password on SMC Router though).
IHR has done a good job pointing you at an informative website so you can set up and configure your Linksys router properly. I personally have worked with Linksys routers quite a bit, and have never had a problem setting them up.
I suggest that you not only change the password on the main router login itself (usually at 192.168.1.1 in a default configured router), but also that you set up the wireless security as suggested. If you do all of that, you will not have to worry about unauthorized persons accessing your wireless.