Are you trying to make a pentagon shaped one (all sides equal) or an odd shaped one ,the easyest way for the latter is to remove a corner from a four sided one and replace it with a fifth side at a 45`angle to the other walls.
For a pentagon shape I would draw out five lines radiating from a centerpoint at 72`angle intervals and use the drawing to figure out the size of walls needed the inside angle of connecting wall should be 108`degrees if i remember my geometry correctly,Hope this helps