Most updates just require you to untar the new distribution over your existing files (application.ini and .htaccess files will not be affected).

If you're using Git, just do a git pull.

However: if the change log indicates that a database migration is required, you need to proceed as below.

Database Migrations

Database migrations are simple. After you update the files, just execute (from the main application directory):

./bin/doctrine-cli.php migrate