You'd use the Drawing Tools, usually located in the lower left corner,
to draw a rectangle or other shape. Once drawn, you can change its
interior color and border line thickness and color.

Most pertinent, once the shape is selected (box handles), you can right-
click on the shape, choose order, and send behind roads.

The shape will have either width & height or vertices.
Vertices will be best to work with because you can obtain
the latitude and longitude.

Also, in code you can .QueryShape.
(I hope you'll find these keywords in MapPoint Help)

Mike Mattys