Having Trouble Configuring WNR3500 As An Access Point

I am trying to configure a Netgear WNR3500 router to be used as an access point.

My AT&T U-Verse Gateway router is in the basement of my house and the WNR3500 is in my office on the second floor of my house. I am using the Netgear Knowledge Base article ID 19852 titled "Set Up a Wireless Router as an Access Point on a Network".

In Step 5 is says in Advanced tab Setup > LAN "In the IP Address field, change the LAN IP address of the router (WNR3500) to 192.168.1.100 (same IP segment of the main (AT&T) router (192.168.1.1) and uncheck the DHCP server box.

I did that and the wireless access point doesn't work.

The AT&T Gateway wireless router IP address is 192.168.1.254. I also tried changing the WNR3500 LAN IP address to 192.168.1.200 and the access point still doesn't work.

I think I am doing something wrong with the LAN IP address.

Can anyone help me configure the WNR3500? This seems so simple but I am stuck.

Thanks, Bill