You can move anywhere in the 'working area' you feel best suited to the play. But!! Remember, you don't want to get too close to "B" because you are responsible for any subsequent play at 3d base (tagup and advance) and you'll be out of position. Use your peripheral vision to see the tagup while you observe C/NC (if its not close to the LF foul line, in which case the PU makes the C/NC). You can see this play from the vicinity of the mound, and then position for the runner's advance to 3d base.
The PU is going to stay at the plate, so you'll have no help at 3rd.