Autocad 15; Print by plot scale (Architect)

Ive been learning AutoCad quite a while now, but i want to know how exactly i use plot scale to print the drawing.

I want to draw in meter.

If the width of a room is 3.5 m, then i shall draw 3.5m line. Without converting it to anything else than meter.(1:1).

So i want to print it 1:100 on A4/A3

How to do this.