Notes:

The banner is outlined in green and the container is outlined in red.
The banner has a cyan background and the container a gray background.

To draw nested Divs (Box inside a box) set the following preferences

and in the AP Elements panel uncheck Prevent overlaps.

Draw the larger container first

Click inside the container and draw the 2nd APdiv.

The reason for nested boxes
will become apparent later...

(parctice, practice, practice)

Select the banner APdiv2 (Blue with its handles)

and type in 960 px for width and 150px for the height Left and Top 0px (zero)

rename apdiv2 as banner

Select the APdiv#1 and rename it wrapper