Dock won't appear on other displays I know, you can't have the dock on both screens at the same time, and I know that there's a 'swipe down' gesture I'm supposed to be able to do with the mouse to make the dock appear. I just can't seem to get that to work, though... I've done this before on other computers. 

Mac OS X El Capitan (10.11) clean install done yesterday.
You can also fix the dock on a other screen:


Go to System Preferences
Click on Displays
Click on Arrangement
Swipe the white bar from one screen to the other


If this won't work, also check the alt + cmd + d keycombination to show / hide the dock.