Q: Different Displays on Mac (Screen)

I have a macbook pro with retina display, and i want to connect a monitor to the mac. When i connected the mac to the screen, the screen is on another desktop (called desktop 2) but in misson control (on the mac) there is no "desktop 2" and when i add a desktop on the mac, the screen becomes desktop 3. How can i control both displays (screen and mac) but with different windows open on different displays on the same misson control?

So basically i want to have a certain window open (eg. preview) on the screen, and at the same time run (eg. google chrome) on my mac without mirroring the 2 displays.

Thank you for your help in advance