Important- You should go to the administration tab (this tab may be different) and set a new password for the administration of your router. Apply the settings after setting the new credentials. This will protect you from having a 'drive by' hack.
On the wireless tab, change the SSID. (the name of your wireless network)
Go to the wireless tab or menu and click on wireless security. As you can see by the above links to emulators that wireless routers will be slightly different. On the wireless security menu, select WPA2 and enter a pass phrase. Make the passphrase complex yet easy to remember. Apply the settings.
On your Windows XP or Vista computer, make sure the wireless card is on and select the appropriate SSID (name for your wireless network). You should be prompted to enter a passphrase. Enter the passphrase and wait for your connection. (Your computer will obtain an IP address after authentication.)
You should now be on the network. If you share a folder on a computer, make sure you only share the folder to a specific user and not to the 'Everyone' group.
Never program your router via wireless connection. Settings can be lost. Your router can be 'bricked' if your computer loses connection during a firmware upgrade.