A personal narrative, and especially the one instructed with this prompt, is a piece of writing from the writer's perspective and own experiences. While writing can be tricky sometimes, I'm afraid only you can do this.
Here are some things to keep in mind though:
Write about something that interests you or you really enjoyed experiencing - this makes the words flow way easier because you're excited to share the moment you're focusing on
Because the instructions say to write of an event important to you, but to write it with you as a narrator and to create a setting and plot, take this exciting moment you want to share and tell it like a thrilling story (like you're telling it to your friends and you really want them on the edge of their seats with excitement). Writing this way can make the narrative come together a lot more fluidly (and way more fun to write).
Because it is a 500-750 word narrative, don't make it bigger than it has to be (both in writing, and how you think of it before you start). Paragraphs can be short, sentences don't have to be complex - don't overthink it.
'Precise, vivid language' can seem a little overwhelming, but think about how you would describe one of your favorite things to a friend. Would you describe the size of it? The color? How it feels, tastes, smells, etc? That is vivid language and shows rather than tells - it doesn't have to be intense, just paints a picture.
