I have fixed it now. I had to guess what to do.
The answer was going to the Network page of the TP LINK and setting the IP to match the Main Router's IP (192.168.0.1). I had to change the TP-Links address to 192.168.0.2 (something about matching it to subnet). Then it that page it also ask me to put in the gateway, and the answer here is to put in the Main Router's IP (192.168.0.1).
Once that is done we must now go to DHCP server page and ENABLE IT!!! This is not on by default!
In there I left Start IP address, End IP address , address lease time as defaults. Now the KEY point here is entering the Default Gateway to your Main Router's IP (192.168.0.1 in my case). AND the DNS server (I had to pull this information from my Main Router's setup page, apparently you get that from your ISP). Then hit SAVE.
After this , go to TP LINK setup page and look for "WIreless Mode" and set it to "Client" and connect that to your Main ROuter. Then go into "security settings" and key in the WEP code that you used to connect to main router. Then press Save.
Still on the TP LINKs setup, go to System Tools and look for REBOOT. Then there, click Reboot. ALl should be done!
They should have made that instruction in their manual which wasn't the case at all. And the FAQ provided needed quite a bit of guesswork as it doesn't talk about DHCP settings at all (or maybe it does but i never found that link!).
Thanks again Shane for posting!