I’m not in front of the box right now, but I believe once you activate the transform tool (Shift + T) in the bottom left hand corner of the viewer, jump over to the video inspector pane and you should find controls for anchor x and Y.
From memory, unfortunately I don’t think there is an on screen control for this to position it in the viewer. You have to adjust the x,y values of anchor in the inspector.
Cheers,
BG