How do I organize my campaign

hello I am new dm. my first session is coming up soon I was wondering if anyone had any tips on how to visualize the adventure. I really need somewhere to write out the story to run. I’m not to sure how to describe but if anyone has any tips I would be very grateful.

side note

this is an in person party that meets once a week this is all our first time playing dnd accept for one person. if anyone needs more specific info I may be able to give it to you