Hi kfaruque.
First of all, what is the brand and model of the accesspoint?
Have you set up the accesspoint yet or just plugged it in?
You need to be sure that the IP of the accesspoint isn't already used on the network, that it isn't running any dhcp server that may interfere with your current network, and that its ip is in the same subnet as your network.
EG:
Network: 192.168.1.1 - Accesspoint: 192.168.1.2 = correct subnet
Network: 192.168.1.1 - Accesspoint: 10.1.1.1 = incorrect.
Cheers