Change background image
Go to menu Edit -> Environment -> Change Background and select a PNG or JPG file.
Edit rooms shape
To edit the map simply click on menu Edit -> Room Edit Mode (F5). Now you can drag the blue handles around to edit rooms shape. The measures are in centimeters. When you are satisfied with your changes disable the edit mode in menu Edit -> Room Edit Mode (F5).
To add new handles double click on a preexistent one. To remove an handle right-click on it.
Add and Delete rooms
To add a new room click on menu Edit -> Room Edit Mode (F5) and then Edit -> Environment -> Add Room. A new square polygon is created on the left top corner of the environment. Now you can drag the blue handles to position the room correctly on the map. To rename the room click on Edit -> Environment -> Rename Room and digit the new name into the dialog box. To delete a room select it by clicking on it then choose Edit -> Environment -> Remove Room.