Move to your AzerothCore sources directory.
If you have your own fork of AzerothCore, you need to sync it.
Otherwise, if you cloned AzerothCore directly from the main repo, you have to
git pull to update it.
Compile again your sources, this step is the same as the Compilation step during Installation, but generally you can skip the CMake part unless you're adding new modules.
For example, in Linux/Mac you just have to
cd build; and run
make -j 8; make install. Of course you can change the value of the
-j paramether according to your CPU.
If you are updating your production environment, BACKUP your databases BEFORE updating them!
You need to import the new sql update files (located at https://github.com/azerothcore/azerothcore-wotlk/tree/master/data/sql/updates) to each database.
To automate this process you can use the db-assembler bash script
If this is the first time you are using it READ THIS FIRST and properly configure your