The bulk of the window is a map. It is recommended that you maximize gametable to get the best use of real-estate.The map is literally infinite.
How to:
Scroll the map: Right click and drag to grab and move the map.
Zoom in-zoom out: The + and - keys zoom in and out, as does the mouse wheel. The furthest-out zoom does not draw grid lines. This is intentional.
Point at the map: Press space while your mouse if anywhere on the map.
A hand will appear in your color (you can see all player's colors in the player list in the lower left).
All players will see this hand. It stays for as long as you hold the space bar down.
Recenter the view for all players: In the "Map" menu, there is an option to "Recenter for all players".
This will set all players' views to be the same thing you're looking at.
Same soom, same location on the map. This is pretty rude to do if you're not the GM.
This feature is needed because with an infinitely large map, some asstard will inevitably get lost in it.
Recenter allows the GM to get everyone (literally) on the same page.
Draw an arbitrary line: Select the pencil tool and click drag to scribble a line.
Draw a straight line: Select the line tool and click drag to make a straight line.
Hold shift while doing this to force it to be vertical or horizontal.
Draw a box: Select the Box tool and click drag to define the box.
Erase lines: Select the eraser tool and drag a rect. Lines will be erased inside that rect.
Erase only lines of a specific color: Select the Color-Eraser tool, (The red eraser) and It will erase only lines of the current color.
Measure a distance: Select the Ruler tool. Click and drag, and you will get a continually updating distance measurement.
Toggle Hex/Grid Mode: Select Map->Hex Mode to change from hex mode to grid mode and vice-versa.