The easiest way, for me, is to use a length of ribbon 1/2" longer for your loops as you did for your bow.
So, if you used 22 inches of ribbon for your bow, use 22 1/2" of ribbon for your loops. Fold it in half, and fold in half again. Crease with your finger where the folds area and voila! Your ribbon is "marked" for your loops.
This post has a great tutorial for surround loops, hope this helps!! http://hipgirlclips.com/forums/how-make/30430-tutorial-how-make-surrounding-loops-easy-way.html#post328728