We took a boat from Plaka (8 euro return) then it was 2 euro to get in. I would have loved to have a guide to tell us about the history but there were none when we arrived so we were on our own. We had a wonderful time hiking up all around to the top with the wonderful views of Crete. It was absolutely amazing all the things that happened on this island. I would highly recommend going in the morning so it's not as hot and wearing good footwear so you can hike around the back/top area of the fortress.
Must Read Before Your Visit: The Island by Victoria Hislop