Problem setting up Zyxel

First of all, how can Zyxel be set up as a standalone router? I was hoping to get rid of my existing Sky router which is slow and has only two ports at the back.
Secondly, the app keeps asking me to connect an ethernet cable to the back, even though it already has one connected. I can't run the set-up past that point. Rebooting the unit makes no difference.

#Others_Nov_2018