I connect my MacBook to a Lenovo C-Dock, which connects 2 external monitors through 2 DisplayPort cables. The problem I have is that the 2 external monitors mirror each other.

I looked at the display settings, and there is no options to change it. I also tried to connect one of the monitor through VGA port, the 2 monitors still duplicate. 

How can I make the 2 external monitors display differently (not mirrored)?