The Rise of Flight Mission Editor is powerful but can be difficult to use at first. This is because when you add a plane or car it won't just work instead you have to use commands that you link to the planes and cars to tell them what to do. It's easy to get confused and not link an object to it's commands in the correct way and this causes newcomers a lot of frustration when their mission doesn't work the way it's supposed to. The only advise I can give is to work through as many tutorials as you can find and if something doesn’t work don't get too frustrated just go back over the steps and figure out what you missed. Once you do become comfortable with the ME you'll find it's very powerful and you'll be able to build almost any scenario you can dream up
These are the tutorials I found useful when learning the RoF Mission Editor.
The official Rise of Flight site useful materials
Download the Mission Editor manual and view the 12 lesson tutorial. Very
useful but the material is a little out of date and doesn’t cover all the
functions now available in the ME. The examples are based on early code so the
maps and some of the dialogue screens may look different to the current
The Manual is not too useful to begin with but is essential as you get to
know the ME. The tutorials are worth completing as they give a good grounding
in the basics.
Vander's Youtube channel
10 videos covering all you need to know to get started.
The2ndbigbang's Youtube channel
3 videos covering the basics of mission editing.