Need to log into the routers web page and go to Setup/Wireless/manual wireless. Change the WiFi mode to something that your device support, i.e. single mode G or Mixed G and N, if you have devices that support N. If you don't and only have devices that support G, then set single mode G. Most devices now days support G and no need to broadcast A and B.
Next go to the Security Mode section and select the drop down menu, probably says NONE. Change the drop down menu to WPA-Personal. Set the Security Mode to WPA2 the Set the Cipher Type to
AES. The type in a password. If you can get your devices to connect after you save the settings, try setting the Security mode to WPA and WPA2 and a cipher type to AUTO.
Also change the routers admin password too under Tools/Admin