Insert the .schematic file in the folder /plugins/WorldEdit/schematics
Go on to your server and type //schematic load “name of file”
Now type //paste -a to paste the schematic that was saved to your clipboard. Please pay attention to your position because your paste will be located depending on it. Also make sure you got enough space.
(NOTE: While pasting a large schematic, your server may crash. To prevent it from crashing, we suggest you to use //fast before pasting or to use method B.)