Router menus and configuration, wireless or not, are accessed by a numerical address. This will be in the manual that you can download online. If you had reset a different address or changed the default password and can't remember it, most routers have a button that will reset it to factory defaults, allowing you to start over. To avoid this situation I now put the address and the password on a piece of tape on the bottom of the router. It's security on the internet you need; your own home ought to be safe enough.
Up till this point, I have used only wired connections to access the internet and know almost nothing about networking- wired or not. I usually use the software firewall that comes in the internet security suite I have at the time.
Then you'll have a menu that will let you choose your configuration options. The manual (or googled instructions) for your brand will also give you the default username and password to enter the conifg. I think for Linksys it's (blank) and admin. For adequate security you should really change those. Then tape them under the router so you can find them again.