@tig said:

You usually get a better response when you post in any tool's main thread...

That said...

It's a 3-point rectangle.
[Read the status-bar prompts]

Click the 2d-rectangle's start-corner. Next click the second-point to set the rectangle's first side [you can also type a dimension + enter]. Finally click a third-point to set the rectangle's second side [you can also type a dimension + enter].
Note in some locales you might use a . instead of a , as the decimal-separator.
e.g. 1.234 >>> 1,234

And also the locale's list-separator changes from a , to a ;

That's not how it works on my SketchupMake2016 (free). I click the first point, then click on the second point and type a number into the measurements box. When I click on the third point I can type another number into the measurements box, but the numbers don't seem to have any effect upon the length of the sides of the rectangle.

When I select the regular sketchup dimension tool, the various boxes I have drawn have no relationship to one another. For instance if I draw a rectangle that is supposed to be 36 units high and 4 units wide and then select the dimension tool, it might show anything from 45 high to 7 29/32 wide. Another box drawn with the same 36x4 dimension might show up as 8-5/32 x 45-1/2. There is just no consistency at all.

I am sure the tool is behaving as it is supposed to, but I just don't understand how to make it draw a box of the dimensions that I want.

vern