Have you ever been assigned a paper and then just sat there staring at a blank page or screen because you didn't know what to write? Many of us have been there at one time or another. My son (whom I will probably write about quite a bit) struggled with ADHD throughout his childhood and still battles it occasionally. One thing I had him try when he was in 5th grade was to write just like he spoke because he never seemed to be at a loss for words around me! You can edit and revise your paper to fix grammatical errors or to make it sound more formal, but to get your ideas down on paper, just relax and tell your story.
Even though he loved to talk, he had a difficult time getting the dialog he had in his head onto paper so I suggested he use a recording device and record his rough draft. He felt kind of funny talking into a recorder at first so I recorded him telling me a story about pirates. He had read a few articles online and a couple of books about real life pirates and wanted to do a report on that for World History. We made his recording and I helped by asking him a few questions to add information. He then transcribed his rough draft onto paper. He was able to edit and revise that for his final.
This method worked for my son, but there are many other writing methods that can help struggling writers. You just have to experiment and find what works best for you!