Different embroidery machines (make & model) have different sizes of sewing fields. You didn't tell us what the make & model of your machine is, so that is the first thing you need to tell us. Also, as far as I know (and I've been known to be incorrect on more than one occasion), you cannot change the size of the sewing field. If you design is too big for your machine, it's too big. Even if the big hoop fits.