Hello XRAAFCHAPPIE,
what scale shall your drawing be? There are small and large harps...
I have added a template for A0 in mm for scale 1:1. This helps to position the drawing into the paper outline. But if you have a different scale you need a different template. In CAD you draw in real size units, scaling in the end is done at printing.
Try out that template for a start ( open it ) and scribble around.
dellus
mech_mm_1_1_a0.dxf