The Blades of Exile Scenario Editor can be a tricky program to use.
It has lots of options and a lot of features.
Fortunately, it also comes with very comprehensive online documentation.
To get to this documentation, run the program Blades Editor Documentation.
This file contains the full instructions for the editor, ready to be printed out.
Of special importance is the section "How to Make a Simple Scenario."
It describes, in exact, step-by-step detail, how to make a simple scenario with dungeons, monsters, and treasure.
This section will give you a quick, easy start.
Once you've mastered the basics, using this section, skim through the documentation.
Unfortunately, this is not a program you will be able to get the best use out of without using the instructions.
Finally, if you're stuck and need ideas, go to http://www.spidweb.com.
There is a Scenario Editor forum there, which has all kinds of hints, tips, and answers for better scenario design.
BLADES OF EXILE - GETTING STARTED