You will generally start an AutoCAD drawing with a template (or previous drawing). The template/previous drawing will have generally have layers, sheet layouts, blocks, and text/dimension/leader styles that will all be useful to you as you are drafting.
Here is a template you can use if you don’t currently have one to use:
If you do need to start a document from scratch, go to New in the A menu in the upper left hand corner, select one of the premade AutoCad templates (usually one that is set up for architecture).
Type UNITS to select the unit type for the drawing. You will generally set up the drawing as Architectural (feet and inches), and set the insertion scale to inches (when you type 6, autocad reads that as 6 inches).
See the Basic Commands Page, or Setting up Paper Space for more info.