You can add translations to local text registry from your application start method.

Sources for these translations might be a database table, xml file, embedded resources etc.

void Application_Start()
{
    // ...
    var registry = Dependency.Resolve<ILocalTextRegistry>();
    registry.Add("es", "Dialogs.YesButton", "Sí");
    registry.Add("fr", "Dialogs.YesButton", "Oui");
    // ..
}

EnumLocalTextRegistration Class

[namespace:Serenity.Localization,assembly:Serenity.Core]

For enumeration local text definitions to be registered, you need to call_EnumLocalTextRegistration.Initialize()_method in your application start:

void Application_Start()
{
    EnumLocalTextRegistration.Initialize(ExtensibilityHelper.SelfAssemblies);
}