This must have taken you forever! Do you have a pattern or did you free hand?
Katie, HDC means Half Double Crochet. Here's a helpful video if you don't know how to HDC http://www.youtube.com/watch?v=LxA2osb5Qfk
Rianne, this YouTube channel is very helpful to people just learning how to crochet: http://www.youtube.com/watch?v=eqca00LdmAc
If all else fails and you still would like a summer mesh hat I'd be happy to make you one. Here's my Etsy link: www.doodlebumpkin.etsy.com