I would suggest that you open the thread entitled "Penn Foster Student Suffering with Oleson Village Map" and specifically go to page 21, the last page, and read the 10th, 11th, 12th and 14th posts. That should get you started. The thread can be found in the AutoCAD > AutoCAD Beginners' Area > Student Project Questions. The same thread, if you start at the beginning, has further information that may prove useful to you as you tackle this project.
Re: Decimal units. "Decimal units are unitless — that is, they’re not based on any particular real-world unit. With decimal units, each unit in the drawing could represent an inch, a millimeter, a parsec, a furlong, a fathom, a cubit (if you’re into building arks in case that rainy day should come), or any other unit of measure you deem suitable, from Danish alens to the Swiss zoll. An example would be 15.5." Source: "AutoCAD for Dummies"
In the case of the Oleson Village Project the units would represent feet.