See those white dots along the walk path? Those are spline handles. The cursor will change when it moves over them. You can grab and move the spline handles to alter the direction and length of the walk path.

You can insert additional spline handles, if necessary, by clicking on an empty section of the path. The cursor will show a little plus symbol to indicate that a handle can be added there.

The walk path is 2D, so it may be easier to adjust by viewing it from the Top camera.