When using a projector with your MacBook, make sure you attach your dongle adaptor first. You may turn on your projector. Then on your Mac choose System Preferences from your Apple menu. Click on Displays. Then make sure there is a check mark in "Shows displays in menu bar". (I choose 1024 x 768 stretched as my resolution. This is your preference.) Then close the window. You should now see a monitor looking icon on your title bar. Click it and choose "Turn On Mirroring". As long as your cables are connected correctly, you should now see the image on your big screen or wall.
