When I work with my students who struggle to put words on paper, I tell them to draw pictures of what they see happening in the story, kind of like a story board. Then add a quick summary of each picture and arrange them in order of however you think they make sense. That should get your juices flowing! Also go online or invest in a good thesarus, these are wonderful for word choice! You may want to investigate 6+1 writing as well. It is a 7 step process for writing and a great way to help you begin.
The steps are:
1. Ideas (jot down your ideas for your story)
2. Organization (put your ideas in order, beginning, middle end, etc)
3. Voice (know your audience/purpose, use words that make sense for your audience/purpose)
4. Word Choice (this is where the thesaurus comes in)
5. Sentence Fluency (do you have long and short sentences, questions, exclamations, etc do your sentences make sense?),
6. Conventions (grammar, punctuation, editing etc)
The +1 is for publishing...how do you want it to look for the reader...good luck!