Firefly Jacket Question

Hi there! I am very very new to sewing and am attempting the firefly jacket for the first time. Would anyone who's made this before be able to help me with Step 4? Am I supposed to sew the elastic/ribbon the right side of fabric A both left-hand and right-hand sides? or is it on the right side of the fabric for the left-hand part of the jacket((as shown in the pattern diagram) and the wrong side for the right-hand side of the jacket? Sorry if this question is too confusing!