It seems you want to know how to control Mesh in Discovery AIM. You can right click on "Physics" tab and select "Define Mesh Manually" as shown below.
Once this is done, an additional "Mesh" tab would appear with the meshing options.
You may like to have a look at this tutorial
to see how manual meshing is incorporated for a structural simulation. Please let me know if this helps or if you were looking for something else.