In order to connect to the Samsung’s is to hard wire via ethernet to the back of each tv. This way you bypass all that WiFi which is not really that great.
on both of our UHD 4K TVs they are connected to my router via ethernet.
of course you will get people telling you they have no issues but trust me unless it’s via ethernet there really is no perfect WiFi connection.
If still looking to connect via wifi, you will need to know the SSID of your network.
after you connect to it via the setup screen on the Samsung you need to put the password in exactly as it was written. If it’s upper case and lowercase then put it in that way. All lowercase/uppercase then put it in that way.