Tried an extender as I cant set up my router. cannot set up the extender either. I need to use Netflix etc Paying for it but cannot set it up????

I know nothing about routers etc and i cannot connect this router. I have an old that came with the wifi provider but it allow me to stream on my TV. I need to connect this one to replace the old one.

Purchased a extender as above but wifi on mobile will not connect. How do I set it up via computer? I am not good with computers etc --Help.