After several years of not having a cover I decided to make one as the machine sits under a ventilation vent(hot in winter; cold in summer) and I felt too much air would dry out the oil in the machine. Anyway, I used one of my practic pieces. I just turned in the edges to make them neater and folded the sides in toward the middle and seamed the end so one end would fit over the front handles of the machine. I let the rest sit over the machine. I'm not sure if many people cover their machines but it probably is a good idea to keep the dust, etc off it.
My practice pieces are made of muslin and/or cheap fabric with batting in between. Width of fabric and about 2 yards long. If using print fabric, use it only on one side and use the muslin side as the top so you can see your stitches. I very seldomn use a practice piece now that I've learned the basics but still have several pieces in the house. I have given some to my neighbor to use for her very large dog.