Press the green button to open the plugin browser on your Zgemma and look for Open Webif.
If it is not already installed, press the green button to go to the list of available plugins, expand the extensions section and scroll down to the Open Webif plugin. Install it.
Exit back to normal TV display.
Press the green button again to open the plugin browser and you should see Open Webif.
Open the configuration popup and click on the enable option to enable it. All other options will probably be OK at their defaults.
Access you wifi router management and look for the ip address assigned to your Zgemma. Set this to a static address if you can.
Open a web browser on your phone or tablet or pc, and enter your Zgemmas ip address into the address bar.
This should open Webif in your browser and give you access to all the channels on your Zgemma and a number of other functions.
You can select the TV channel that you want and your Zgemma will switch to that channel.
Hope that I have described everything correctly, but I have not got access to mine at present. I will check later.