@maryoom17776 

May I know how you set up your range extender? 
1. If you set it up by using WPS button, your extender would copy the Wi-Fi name and password from your main router. So, on your wireless client devices, you would only see one Wi-Fi name which is exactly the same as your host Wi-Fi. The only difference is that your existing WiFi signal would become stronger and that is how extender works.

Thus, please feel free to connect the router WiFi network and check if the signal strength is improved.

2. If you set up the extender by using the web interface or Tether App, during the configuration, if you checked COPY HOST NETWORK, the WiFi name of your extender would be exactly the same as your main router as well. However, if you set a different Wi-Fi name for your range extender during configuration manually, you should be able to see the new WiFi network on your wireless client devices.

3. If you are still able to manage the extender on Tether App, please go to TOOLS---EXTENDED NETWORK part, then you could change the Wi-Fi settings of your extender into a different Wi-Fi name.