RE:Good Grief Charlie Brown!
It sounds like you have the tools you need, but you just need a way to get at the story.
Do you have the plot worked out? If you do, you might try something that has worked for me: Put a one-sentence description of the key scenes or conversations at the top of a page (you may find it easier to try handwriting this until you get going). You have a starting point.
Then start to write the scene or the conversation so you can get the action going. You don't have to start at the beginning of your story and you don't have to make yourself write all the way through the scene. Just get a couple of paragraphs down and move on to the next key scene on a new page. This way, you can start to form a skeleton of the story and can flesh things out from there. I've found it helps me quite a bit, no matter what kind of writing I'm doing.
Here's an article on our website that offers some great tips, too: "Break through writer's block" by Michael Banks.
I hope this helps!
Martha Lundin, editorial associate for The Writer