2D shapes are the easiest way to create circles and ellipses. Available in the Sketch menu, tap on the shape you need and start placing them with your Pencil.
Create a circle by tapping on the Circle tool. Put down the tip of the Pencil on one point and start dragging. You will notice that a Circle appeared. Once you are done, tap on the dimension label to define its radius.
Create an ellipse by tapping on the Ellipse tool. Same as with the Circle, just put the tip of the Pencil down and start dragging. Once you are done, you can define the major and the minor axis as well.
In Shapr3D an ellipse is defined by its center point, its major and its minor axis.