That isn't a lot of help when I want to create a new drawing! If you can't set a scale before starting a drawing what use is it in the field?

I just downloaded Sweet Home last night. I am not using it for home design at the present. What I am trying to do is draw infill walls in an attic space, exterior stairways and other misc. details. Before drawing I would like to set my scale for 3/4" to the foot. How do I do this?