Is there any computer connected to the router ?
If not then you will need to connect the computer to the router.
Do not change any wireless settings on the router with the wireless computer.
you will need to connect the computer to the router with the Ethernet cable.
check the IP address of the computer.
open the router set up page of the router.
Here you can change the wireless settings of the router.
Now once you change the network anme and security on the router, you will need to connect to the wireless network on your wireless computers.
Click Here for step by step instructions