How can I add a laptop to my home network?

I had a home network set up by experts because I usually have trouble with technology. They said I could add more peripherals anytime I wanted by providing the network name and password. But my laptop doesn't give me a place to provide this information. It knows the network is there because it recognizes the network name and gives me a message saying "Windows was unable to find a certificate to log you on to the network XXXX" (With the XXXX being the network name.) I've looked all over for a way to give the machine the password, but I cannot find a place to do so. I've checked the control panel under "Network and Internet Connections" and nothing there asks for passwords. Of course, the laptop won't connect to the internet, so it is not on my home network. It sits there with the "certificate" message or one that says something about trying to "verify." I've even tried using the network installation CD in the laptop and looking for something there which would allow it to connect, but that, too, has not worked. What is this "certificate" which the laptop is looking for, and how can I give the password and allow the laptop to communicate with my home network?