ForeignKey and Classes

How do you retrieve a specific object from a class using a ForeignKey?
I created a class called TryoutJersey with three objects.

class TryoutJersey(models.Model):
  jerseyColour = models.CharField(max_length=50, blank=True, null=True)
  jerseyNumber = models.IntegerField(unique=True, blank=True, null=True)
  jerseyDescription = models.CharField(max_length=50, blank=True, null=True)
  def __str__(self):
      return self.jerseyColour

and I want to assign a jersey to a player in my player class using a ForeignKey.

tryoutJerseyNumber = models.ForeignKey(TryoutJersey, blank=True, null=True, on_delete=models.CASCADE, related_name='JerseyNumber')

How would I do this? The jersey is a single item with a color, a number and a description. Should I have some unique identifier other than those three items to tie to the player and return that? What would that be? Wondering what others would commonly use. Like a part number I suppose. Is there a number generator that people use? I’m stuck here. I want the TryoutJersey class for the admin section so I can add jerseys. They tend to change from season to season. Not sure what to do here.
This is really more if a database question than a Django question I think.

So assuming you have some other model:

class Player(models.Model):
    tryoutJerseyNumber = models.ForeignKey(TryoutJersey, ...)

then, if you have an instance of Player named a_player:
a_player = Player.objects.get(id=1)

You access the members of TryoutJersey using the object reference notation on the referencing object:

player_jersey_number = a_player.tryoutJerseyNumber.jerseyNumber

Or, if you’re creating a new TryoutJersey and want to assign it to a_player:

tryout_jersey = TryoutJersey(jerseyColor="Blue", jerseyNumber="30", jerseyDescription="Whatever")
a_player.tryoutJerseyNumber = tryout_jersey

See Many-to-one relationships | Django documentation | Django for more details.