Adding translated fields to an existing model

Create a proxy class:

from django.contrib.sites.models import Site
from parler.models import TranslatableModel, TranslatedFields

class TranslatableSite(TranslatableModel, Site):
    class Meta:
        proxy = True

    translations = TranslatedFields()

And update the admin:

from django.contrib.sites.admin import SiteAdmin
from django.contrib.sites.models import Site
from parler.admin import TranslatableAdmin, TranslatableStackedInline

class NewSiteAdmin(TranslatableAdmin, SiteAdmin):
    pass, NewSiteAdmin)

Overwriting existing untranslated fields

Note that it is not possible to add translations in the proxy class with the same name as fields in the parent model. This will not show up as an error yet, but it will fail when the objects are fetched from the database. Instead, opt for reading Making existing fields translatable.