When world building, writers should have detailed notes about the world created. You need to be able to see it, hear it, smell it, taste it, feel it.
You also need to be able to pull readers in through subtext, background, and dialogue—not lengthy exposition.
You need to know its landscape, architectures, languages, religions, hierarchies, and magic systems. You need to know its technology, industries, professions, and means of transportation.
What socioeconomic classes are represented? What’s school like? Are there police? What’s a family look like? When do citizens reach “adulthood”? What and how do they celebrate? What does death look like? What motivates the people of your world?
How many seasons are there? What animals run amok on land? In the water? What foods are common? Drinks? Do they appreciate art? How do people in your world feel about magic? Are there limitations?
Have a spreadsheet or document where you record all of these details to refer back to as you write. Not only will this ensure consistency in your storytelling, it will also (hopefully) result in a confidence in that world that translates to the page.
In the end, you shouldn’t explain more than maybe 10-15% of this outright. The rest—or what’s important about the rest—will come through in how your characters speak or interact with one another, in what they experience, etc.
