How to change stitches

Question

I have a Necchi 535FA and no manual. I need to know how to use stitch number 6 at the moment. Right now it is straight and tight but neat. It was my Grandmothers and this is the first time I have tried to use it. I found how to thread it online and so that part is done correctly. I just seem to have a problem getting the right combo for the stitches.