That is such a nice looking machine.
I have a Kenmore 8 Stitch Sewing Machine Model 158 13450,it looks a lot like you machine. When I want to do a decorative stitch I turn the knob to the stitch I want then how wide I want the stitch to be. for ziz zag be sure to have you ziz zag foot on or you could brake something. Does it have a feed dog lever to raise feed dog up and down like when you are doing free motion quilting? Mine just has a cove plate to cove feed dog.
Also I know mine does not fit in a cabinet (wish it would) just portable case. You are lucky someone gave you a nice machine like that.