@Gally 

Hi,

If you mean you see a Wi-Fi network named "TP-Link_Extender" and upon trying to connect to it you are told the connection is not secure, then this is normal. And it would also mean the Wi-Fi extender has not been properly setup yet.

Can you please tell which steps you have performed so far to setup the Wi-Fi extender, so that we can get an idea where it might have gone wrong?
 

  @woozle  thanks for your reply.

I have followed the 4 steps given on the installation guide. 1. Downloaded tether. 2. Launched the app and set up an account. 3. Tapped the + to add. 4. wasnt given any further instructions so you are probably right that it isn't properly set up. If I don't get it sorted soon it us going back to amazon.

  @Gally 

I can't tell why the Tether app didn't lead you all the way through the setup. I rarely use it myself.

In my opinion, the easiest way to connect a TP-Link range extender is by using the "WPS" method.

Does your Wi-Fi router have a button labeled "WPS"? Most routers designed for home use have such a button. Depending on the router model it may be located on the top, rear, sides or front.

If so, then press the "WPS" button on your Wi-Fi router and right after that press the "WPS" button on your TP-Link range extender. It is very common that one of the LED lights on the device starts blinking, giving the user a feedback that the WPS process has been initiated.

After a while those LED lights should turn solid on again. If the whole process was successful, then the Wi-Fi network with the name "TP-Link_Extender" should disappear and instead new Wi-Fi network(s) should appear that are named like your router's Wi-Fi network(s), but with a trailing "_EXT" ending. These are the extended networks of the TP-Link range extender. The passwords will be the same as the passwords for the original networks of your Wi-Fi router.

By the way, some Wi-Fi router models also use dual-function buttons, for example "WPS/Wi-Fi", where a short-press of the button triggers one function and a long-press triggers the second function. In such a case you might need to consult the user manual to be sure what does what.

Furthermore, if your Wi-Fi router happened to be also made by TP-Link and supports "OneMesh" or "EasyMesh", then connecting a "OneMesh" or "EasyMesh"-capable TP-Link range extender via any of the supported methods would lead to the creation of a Mesh network instead of a normal range extension and you would not see any Wi-Fi networks with an "_EXT" ending.