For making a rectangle please select the ‘Rectangle Tool’ . You can make the rectangle in the same way as drawing a line.
To edit the rectangle, click with the right mouse button on the rectangle. A menu appears. If you select ‘Border Style’ you can change the border and the colour of the border. With ‘Background’ you can edit the background of the rectangle and with ‘Shadowing’ you can make a shadow off the rectangle.
If you want to place the retangle in the background and a field in the foreground, use CTRL+B.