You want 5 inch strips the width of the fabric for the front band and 2 inch strips for the armhole bands.
Lay it along the front edge of your jersey you just sewed.
You might need to sew two strips together to make it long enough if so do that. Cut a length the right side for the front.
Next lay it around the armhole and cut to the right size. Make a tube for each armhole by sewing the short ends together. Repeat for the other side.
Iron each piece in half and then sew (or serge) to the jersey.
You should now have the basic jersey made. All that is left is decorating it.