Give Centre Point:
Select the centre point (P1) of the ellipse using any of the snaps and input options. The prompt now reads:
Give Major Axis Point:
After selecting the centre point a dynamic line is drawn from it to the cursor. This line represents the length and angle (A1) of the major axis. Select a point (P2) using any of the snaps and input options. The prompt now reads:
Give Minor Axis Point:
Again a dynamic line is drawn from the centre point to the cursor. In addition to this the ellipse is also drawn dynamically. Now only the Minor axis length needs to be set. This length (D1) is measured from the cursor (P3) position perpendicular to the major axis (see examples below). Select a point using any of the snaps and input options and the ellipse is drawn.
See Modifying/Moving a Ellipse for information on how an ellipse can be edited.