If you've built something in Minecraft and want to save it to a schematic file to share with friends or the internet, do the following: schem load How to make a schematic file? This command also comes with a handy load button next to each schematic, which replaces the load command above.
If you want to see all the available schematics, you can use the /schem list command. If you've downloaded a Minecraft schematic file and want to load it into your Minecraft world, do the following: If the schematics folder doesn't exist, make a new folder named schematics. On Forge and Fabric, this is inside the config folder. On Bukkit-based servers, this is inside the plugins folder. WorldEdit stores schematics in the worldedit/schematics folder. If you're a developer and are looking for the tutorial on the API, see here. WorldEdit is one of the easiest ways to import schematics into Minecraft.
There's been a recent uptick in people wanting a correct tutorial on using schematics in Minecraft with WorldEdit, due to a few incorrect tutorials floating around the internet.