As @secretfarmerGal says, maybe get used to the world map first. By default, the scroll wheel on you mouse will zoom in and out. Zoom right into the airport for departure and you’ll see the runway layout and all of the parking spots. Pick one and select it as the departure. Next, select the destination. You can use the mouse wheel an world map again, or if you know the ICAO code for the airport you could put that in the search box in the destination window.
Let us know how you get on.