Photoshop is quite an extensive programme and you won't be able to make an amazing poster from the start. It takes practice to get to know all the buttons and actions etc. Now what I'd recommend is looking up tutorials online to get familiar witth the basics. I myself have photoshop cs5, so I don't know what cs6 looks like, but I do recommend you checking this out.
www.asianfanfics.com/story/view/71271/indesign-constructing-your-creativity-graphics-original-poster-random-tutorial-resource

They made a 'fic' with a lot of useful tips and tutorials on how to make a fanfic poster. I'm pretty sure they use cs5 as well.. So I don't know if the layout is the same as in the photoshop version you have, but most of the features should be the same. ^^ And just remember, practice makes perfect!