13.134.60.54/32 on your database port (usually 3306 for MySQL). This is the step most people get stuck on — if your database is on a hosting provider, the setting is usually called remote access, allowed hosts, or trusted sources.Please note, you should always use a database user that is scoped to the minimum necessary permissions for what you want your users to be able to do within Redbrix. For example, if you don't want your users to be able to delete records, you should create a database user without the DELETE grant.
Setting up covers each step in more detail, along with database user permissions and what to check if a connection fails.