Here are some tips to point you in the right direction:
-Find the measurements using the 2D viewer. Measure Left to Right and bottom to Top.
-In this example I set the Fixed Shelf Dado to "0"
-At the Interior tab, split vertical 5 times
-At the first opening on the left split horizontally 5 times using "Fixed" shelf
-Select the bottom shelf, click the "Adjust part" and add a the necessary amount to reach the right end (Ex, 47.3898")
-With the same shelf still selected click on the "Edit" button
-At the Editor, add the necessary points to the edge according to the measurements taken before. Since you measured left to right it will be easier to place the points from the X axis reference.
-To apply this shape easier and quicker to the other parts, save the Shape to library
-Select the 2nd shelf, adjust the Right Edge.
-With the same shelf still selected click edit and "Load the Shape from Library"
-Repeat this process for shelves 3 and 4
The process from this point forward is basically the same on the Partitions only that you skip the "Adjust Part" and go directly to the "Edit" button
(See Images below)