You can do this in three steps.

1) Draw a projection of your yellow line on the x-y plane, and also a line perpendicular to it (they are shown as blue lines). Also draw the green line in the image on the x-y plane.

2) Use the rotateaxis command to align your face as desired, as shown in the second picture. You should select the end points of the vertical green line as the axis to rotate about.

3) Use rotateaxis one more time, this time selecting the endpoints of the horizontal green line as the axis. Select the appropriate angle by picking the end of the vertical green line as the first reference, and the end of the yellow (orange in the picture) line as your second reference. The face normal is now aligned with the yellow line.

Dan