How to save data to a Django model in views.py?

I am trying to create an e-commerce site (CS50 Project 2) that allows the user to add a listing, created through the Listings Model, to their WatchList. I am using a Django form with a Boolean field. I need help saving the listing to the WatchList Model. Also, since there will be more than one WatchList because of the multiple users, should I implement Sessions, and if so, how do I do that?

views.py

def listing(request, id):
    #gets listing
    listing = Listings.objects.get(id=id)
   
    watchlist_form = WatchListForm()
    watchlist_form = WatchListForm(request.POST)
  
    if watchlist_form.is_valid():
        watchlist = watchlist_form.save(commit=False)
        watchlist.user = request.user
        watchlist.save()
        return render(request, "auctions/listing.html",{
            "auction_listing": listing,
            "watchlistForm": watchlist_form
        })
    else:
        return render(request, "auctions/listing.html",{
            "auction_listing": listing,
            "watchlistForm": watchlist_form
        })
    return render(request, "auctions/listing.html",{
        "auction_listing": listing
        "watchlistForm": watchlist_form
    })

models.py

class Listings(models.Model):
    CATEGORY = [
    ("Miscellaneous", "Miscellaneous"),
    ("Movies and Television", "Movies and Television"),
    ("Sports", "Sports"),
    ("Arts and Crafts", "Arts and Crafts"),
    ("Clothing", "Clothing"),
    ("Books", "Books"),
]
    title = models.CharField(max_length=64)
    description = models.CharField(max_length=500)
    bid = models.DecimalField(max_digits=1000000000000, decimal_places=2)
    image = models.URLField(null=True, blank=True)
    category = models.CharField(max_length=64, choices=CATEGORY, default=None)
    user = models.ForeignKey(User, on_delete=models.CASCADE, default="")

class WatchList(models.Model):
    listing = models.ManyToManyField(Listings)
    user = models.ForeignKey(User, on_delete=models.CASCADE, default="")
    add_to_watchlist = models.BooleanField(default=False)

watchlist views.py

def watchlist(request):
    watchlist = WatchList.objects.filter(user=request.user)
    get_listings = watchlist.listings.all()
    listings = get_listings.objects.all()
    #listings = [listings.title for listings in watchlist.objects.all()]
    return render(request, "auctions/watchlist.html",{
        "listings": listings
    })

fixed views.py

def listing(request, id):
    #gets listing
    listing = Listings.objects.get(id=id)
    watchlist_form = WatchListForm()
    if request.method == "POST":
        watchlist_form = WatchListForm(request.POST)
        if watchlist_form.is_valid():
            new_watchlist_listing = watchlist.listings.add(listing)
            WatchList.add_to_watchlist = True
            return render(request, "auctions/listing.html",{
                "auction_listing": listing,
                "watchlistForm": watchlist_form
            })
        else:
            return render(request, "auctions/listing.html",{
                "auction_listing": listing,
                "watchlistForm": watchlist_form
            })
    return render(request, "auctions/listing.html",{
        "auction_listing": listing,
        "watchlistForm": watchlist_form
    })

source https://stackoverflow.com/questions/72411422/how-to-save-data-to-a-django-model-in-views-py