how can I write a narrative about a spaceship landing in my yard?
1. Write it in first person -- that is, write it from your own point of view. The story will have lots of instances of forms of "I" and "me" in it, that that "I" will be you!
2. Write it in chronological order -- that is, from beginning to end.
3. Use LOTS of details, lots of color, sound, smell, etc. (the 5 senses), in your story. The more really clear details you can use, the better your story will be.
4. If you're having trouble getting started, close your eyes for a few minutes and imagine such an event. Then take a sheet of paper and just write down what your mind "saw" when your eyes were closed. This should be freewriting -- content only -- don't worry about grammar, capitals, etc.
Let us know what you come up with!