How do I add a table limited to only one row in mysql/django?

I'm using Django for a small project and I want to make a table with one row to add the description of the project in it. I only need one row and nothing more since it's one description for the whole site and I don't want the user to be able to add more than one description.

I solved the problem with the following code

Class Aboutus(models.Model):
    ....

    def save(self):
        # count will have all of the objects from the Aboutus model
        count = Aboutus.objects.all().count()
        # this will check if the variable exist so we can update the existing ones
        save_permission = Aboutus.has_add_permission(self)

        # if there's more than two objects it will not save them in the database
        if count < 2:
            super(Aboutus, self).save()
        elif save_permission:
            super(Aboutus, self).save()

    def has_add_permission(self):
        return Aboutus.objects.filter(id=self.id).exists()