Can't connect to wireless network with Macbook Pro

Hi Mac Experts,

I got a new MacBook Pro (MBP) just 2 days back.
I am trying to connect it to the wireless network at my home.
I am using 2 other dell laptops on the same network and they could connect to the internet without any problem.
But this MBP doesn't connect to the internet. If I click on the Airport symbol on the top right hand side of the monitor (Grey Colour Arcs), it shows that it has connected to my network. But if I open Safari browser, nothing happens.
I checked for the ip address in system preferences -> Network -> TCP/IP and it has acquired an ip address.
My first dell Laptop has ip address xxx.xxx.xx.40, my second dell laptop has xxx.xxx.xx.41, and my macbook pro has xxx.xxx.xx.42 as ip address.

If I go into "Network Assistance" and I look at the left hand side, it shows that
Airport -> Green Light,
Airport Settings -> Green Light,
Network Settings -> Green Light,
ISP -> Green Light,
Internet -> Red Light,
Server -> Red Light.

if I switch on my second dell laptop and MBP at the same time then my second Dell Laptop shows a message that "The ip address conflicts with another computer on this network" and the internet is getting disconnected on this 2nd Dell laptop.

Still my MBP couldn't connect to internet.
So, can anyone please help me to get rid of this issue?
Your help will be greatly appreciated.

Thank you in advance

I would make sure your encryption on the router/modem is set to WPA2 and then
click on your wireless icon and click ask to join other network yor network should show
up then prompt you for a password.

Hello,

Thank you very much for your reply.
I've provided my password after joining the network.
The system shows that it has connected to my wireless network.
But internet is not connecting.
And one more thing is that if I switch on my Macbook Pro, the internet connection on one of my dell laptop will be dropping saying that "Clash of IP address with another system on this network".
I made my MACBook Pro to select manual IP address. (under "System Pref. --> Network --> TCP/IP--> Select DHCP Manually--> Set IP Address").
But no use, I couldn't connect to internet.
As I mentioned in the post above the signal lights are:
Airport -> Green Light,
Airport Settings -> Green Light,
Network Settings -> Green Light,
ISP -> Green Light,
Internet -> Red Light,
Server -> Red Light.

Looking forward to answer which can connect my macbook pro to internet.

Your help will be greatly appreciated.

Best regards