You have your map-grid in front of you. Double-click to create location, click on location to pop up location window, create everything in or about that location (objects, NPCs and all their commands and tasks) with drop-down menus within the location window. Click and drag to make pathways to other locations. Repeat a few times and you’re good to go.
Click bottom of description window to create alternative description. Use drop-down menu to select conditions under which alternative description should be shown to player.
Make that two of us.