How to implement a form to add a video using M2M m

Question

I have this model from this question:

class Category(models.Model):
    category = models.CharField(max_length=50)

    def __str__(self):
        return self.category

class Tag(models.Model):
    tag = models.CharField(max_length=50)

    def __str__(self):
        return self.tag

class Video(models.Model):
    title = models.CharField(max_length=255)
    categories = models.ManyToManyField(Category, through='Taxonomy', through_fields=('video', 'category'))
    tags = models.ManyToManyField(Tag, through='Taxonomy', through_fields=('video', 'tag'))

    def __str__(self):
        return self.title

class Taxonomy(models.Model):
    category = models.ForeignKey(Category, on_delete=models.CASCADE, null=True)
    tag = models.ForeignKey(Tag, on_delete=models.CASCADE, null=True)
    video = models.ForeignKey(Video, on_delete=models.CASCADE)

How should I implement a form that let me create a new video, with their associated categories and tags using these models bearing it mind it has and intermediary table using through_fields ?

NOTE: Use edit history (revisions) to see the previous questions before I reworded It.