Confusion between setting the size of something, aka its “dimensions”, and adding the annotation called “dimensions”.
this does not work on my version. You can use the move tool and select the rectangle, but you can not enter into the Dimension field to enter a value…
Very frustrating…
Once you start moving the edge of the rectangle you can type the distance you want it to move.

Thank you for being patient, this is really frustrating to me. I use to teach AutoCad 9-12 for years back in the late 80’s through the 90’s…
I erased the darn rectangle and started over. What I figured out is that you can’t click into the measurement/distance window, you simply start the rectangle and start typing the x,y coords you want.
Simple if you slow down…
Neo
This is the key. There is never any reason to click in the measurements window. If it’s available for input, just start typing. Also notice that the label for the Measurement window will become specific to indicate what it is expecting you to type.
Also note that as long as you don’t change tools or start drawing a new entity, you can change your mind as much as you want.

In this sense the measurements box is similar to the command line window in AutoCad. You don’t click into that either.