Using extended vs. mirrored monitor/display with MacBook Pro

I have a MacBook Pro (15", 2016) on OS Catalina 10.15.7. I would like to be able to use a large screen monitor as extended NOT mirrored to my laptop. I have an OKX mini-hub/docking station with an HDMI cable and basic Acer monitor.

I cannot figure out how to find/change this setting to use the "extended" function vs. mirrored. What am I doing wrong?