1998 Buick Century 86000 miles

I'm having a problem with only the driver side wiper. The wiper doesn't stop once it reaches the top, it continues right off the windshield and then back on the windshield stopping half way down. I stopped the car and manually returned it to the starting position. How do I fix this problem?

The wiper blade arm should come off so you can readjust it. It is usually held on with a clip at the end of the arm so you can adjust it when needed, or if you had to replace it you could take it off also. Should pull straight off the pin it is on.