Hi,
You enter the dimensions at the Command Line. This is at the bottom of the AutoCAD screen. When you envoke a command, a message promt (different for all commands) appears at the command line. This ask/tells the user what to do or where they want the entity etc..
As a newbie, you should always read the command line, as it's a sure-fire indicator on what the program is doing or is asking you to do.
When you envoke a command, for example the Rectangle command, you should see the following at the command line:
Command: _rectang
Specify first corner point or [Chamfer/Elevation/Fillet/Thickness/Width]:
...Here it's asking you to select a point for the first corner. Now you can select the point in two ways. By poicking the point with the mouse on screen, or by entering a co-ordinate, then simply select the opposing corner of the rectangle by the same method(s).
You'll notice that the command also prompts for some more options. For example, Fillet (type F and press enter) here you can select if and how much you want to round the corners of the rectangle..
But anyway, enough babble! To get more info, simply search the Help system within AutoCAD - there's loads in there to help, from the most basic to the advanced stuff..
If you need anymore help, don't hestitate to use this forum as much as you need or feel free to email me on the address below - I'll be pleased to help you..
Good luck,
Cheers,
Renegade.. BULLET-PROOF DESiGNZ
renegade@tiscali.co.uk