Instructions
Open your game and click the lot you want to expand to enter the in-game controls.
Press "Ctrl" + "Shift" + "C" to open the cheat console.
Type "biggerlotexpander on" to turn the lot expansion feature on.
Go to the edge of your lot in the direction you want to expand and right-click and drag to increase the lot size.
Turn the cheat off by pressing "Ctrl" + "Shift" + "C" to open the cheat console again and type "biggerlotexpander off" to turn the lot expander off.