you have to change the display settings , go into system preferences , then "monitors" or "display", i don't exactly remember but you should find it easily, then you have to change the configuration of what is displayed on each screen , for that you got an option that will display a schema of both your screen and you're able to move the white top bar that is inside your main screen to the other one .

The screen with the white top bar will be the one that will display both the dock and the white top bar

i hope you will understand me but it's pretty hard to explain it , as i don't have my mac in front of me , and english is not my mother language