The bagua is considered the "map of feng shui." It is designed to help you figure out which parts of your home correspond to each of the nine areas of your life.
How do I use it?
Each different colored area (or gua) corresponds with one of the life areas. To overlay the bagua on your home or work floor plan, stand at the threshold of the architecturally intended (not the one you happen to enter most often) front door facing in and hold the diagram so that the blue, black and gray guas are closest to you. Pretend you can draw a line straight across the front of the home where the door is: that would be the line at the bottom of this color chart. Now that you have the correct orientation, just divide your space up into nine guas as if you were cutting a square cake up into nine pieces. It helps to think of them as nine squares for this exercise -- like a little tic-tac-toe board overlaid on your house.
What if my front door isn't clear?
A lot of people at this point feel that they can't go on because their door is at some strange angle or is confusing for some other reason. If you are confused about the front door, then just do each room individually using the door to that particular room as the starting point to overlay and orient the bagua.