You will have to play with it some. This should get you started though
Open the TE
File > New
Type the name of your map (must be 8 characters or less)
start off with a 64x64 map since it is the smallest.
To place a tile (grass, forest, etc.) select a grid and in the upper right of the TE click the type of tile you want and then click "set type" (you can select many tiles at once)
This Thread should help you with placing different fields.
This Thread will help you with placing task groups.
to make a clipboard map:
open your map in the terrain editor.
Click File, make map
Then open the bmp created called map in a paint program (I suggest something other than MS Paint)
Create a new folder in your terrain folder called texsrc
Save the bmp you opened in the texsrc folder, make sure it is saved as 256 color (8 bmp).
also make sure when you save it in the texsrc folder it has the same name as your .oba file.
Any other textures/skins will also be placed in the texsrc folder, but they have to be saved as 256 color or they will not show up.
When you are done with everything and you're happy with your terrain, close the TE (make sure to save) and open it again.
Click File, Build
This will build your terrain as a.res file, it will show up in your ah2editor>ahiiterr folder. You will need to copy/cut it and move it to this directory, c:/programs/HTC/Aces High II/ahiiterr/
Now it will show up in AH
That is a
very basic how-to.