add password to or disable network

[pursuant]

This was set up by a friend who is no longer available to assist me with this. I have two networks set up in my house, one is invisible, you have to know it so you can log into it. The other is a "guest network" that has no pw, you can just jump in. I would like to add a pw to it or disable it so i have some control over who uses my connection. I get my internet through a comcast  and have a Linksys router. I have been in my setting in the control panel and network sharing options but can't figure it out. If anyone can help I'd appreciate it.

Thanks
Mark

[BC_Programmer]

Typically router settings are dealt with using your browser. Typically, the router will be accessible by going to http://192.168.0.1 or http://192.168.1.1

However they have another username/password combination.  Unless they left it for you, that could be a problem.

[Geek-9pm]

Look at the bottom of the router.

[Geek-9pm]

What is the model number of the router.

[pursuant]

 Linksys model BEFSR81 ver 3