Maya places vertices on the ground plane unless you snap them to existing geometry.
Click to place the next vertex. Maya creates an edge between the first point and the last point you placed.
Place another vertex. A dashed edge connects the three vertices.
Do any of the following:
Press to finish the polygon.
Press to delete the last point you placed.
Press y to start a new polygon.
Continue placing vertices to create a quad or n-sided polygon.
To switch to editing vertices, press Home or Insert. A manipulator appears on the previous vertex. Use the manipulator to
move the vertex, press Delete to delete a segment, or click another vertex to edit it. Press Home or Insert again to finish.