you said you had downloaded the manual for your router. It
tells you how to reset it to factory defaults. In my experience, some routers
are difficult to reset; you need three hands, and you need to hold something
awkward for 15 seconds.

It's easier to set up a router the first time if you are wired to it, not by
wireless. Set it up to use WPA encryption and give it a strong password. (WEP
encryption has been cracked.) And give "admin" a strong, different password.

Whether you are using Linux, Windows or OSX, your computer does not have any
software that is specific to your *router*. It does need software for the
wireless adapter in the computer, and in many cases, that software is included
in Linux. There are videos on youtube about how to connect, assuming your
wireless adapter "just works."