AirParrot 3 can be used as a menu bar application, which appears at the bottom right of the screen near your clock.
If you have a lot of menu bar applications open, it is possible that the icon may have been hidden due to space. Try clicking the "expand" arrow in this menu to show more icons.
We've created a guide for setting up and using AirParrot for the first time. The guide includes photographs and step-by-step instructions. You can find the guide here.