Well, i kinda want to write my own mythology story, like a sci-fi type one, do you guys have any advice on how i can write a sci fi mythology story

Let your imagination flow, do some research on whatever time period the mythology you're interested came from, pick up a few books.

When writing a story based upon Sci-Fi or mythology it is best to build the world first. Let the conflict build around the world the characters live in.

Research myths, see how they come about and why, see how it reflects their society.  Myths reflect the society that made them.  They created the myths as their explanation for the way things work.  For ideas, research individual myths and get a feel for them, and develop your world more.  What use would your world have for these myths?

Pretty much what everyone above this said, but I would like to say that I find it to be very easy to overuse the use of details on that kind of stuff. Doing so will result in to much filler. That doesn't mean to avoid using details completely, far from it, details can be the icing on the cake in a mythology. Yet, I personally have gotten carried away in the past.

I usually just take time to think. if it helps try to dream about what it is you want to write about and record all of your dreams. 

That is what I do.

Well, i kinda want to write my own mythology story, like a sci-fi type one, do you guys have any advice on how i can write a sci fi mythology story

 

Open up a word document and start typing. Good luck!

Play some Final Fantasy and get inspired.

Build it organically. Don't have anything just appear out of nowhere (things like kingdoms or empires). Show how things become developed and established. If there are tribes and factions, show how they appear and grow.