Hooping hats with a regular home embroidery machine is not easy. You do need a special insert that, at least on all the machines I've used, will fit in the 5 x 7 hoop. The insert comes with instructions.
I do embroidery for people all the time but will only do hats for a very special few, mainly family, because it is so tricky.
Not saying you can't do it, just be aware and have a couple of practice hats - I buy them at Wal-Mart for around $3.