How to find out dimensions

I am very new to 3D work, as in this is my first 3D programme I’m ever using so please be patient with me, and hence I would deeply appreciate your help.

When selecting the area of the model, how would I find out the dimensions (as shown in attachment)?

Hello- BoundingBox should help - it will print the overall dimensions at the command line. If you set Output=Curves, this is handy for adding dimensioning to the model as well, (Dim command)