We need to define some terms here.
"Parking" is movement from west to east, done slowly over a period of 30 minutes to an hour. It is done after the sun goes down and after the west limit has been reached, when there is no sun to track. "Tracking" is the movement from east to west, following the sun.
If your tracker parks in the west after dark, you need to flip the circuit board upside down, then it will park in the east. The components on the circuit board should point up, or north, depending on your perspective.
If your tracker does not accurately track the sun, then you might have other problems which are hard to determine without more information. I would make sure the board is properly mounted, the linear actuator somewhere in the middle of it's travel, then apply power to the board on a clear sunny day and observe the behavior.