Put the router withing 20 feet and be sure nothing odd like hidden SSID or MAC filters.
We cover all that in the CNET Networking Forums "Samsung owners start here" sticky post.
I may not write all that is there in every reply to folk asking for wifi setup help.
My new 6900 LED TV will not connect to my wifi. I have had my internet provider walk me through changing IP address etc. Nothing. My Samsung tablet and laptop are working fine off the wifi. My provider tech support was on an online page like this and mentioned lots of people were having this issue. I was not home when Best Buy delivered the TV. I am annoyed they left without making it work.