class CsvImportForm(forms.Form):
  csv_file = forms.FileField()
@admin.register(Hero)
class HeroAdmin(admin.ModelAdmin, ExportCsvMixin):
  ...
  change_list_template = "entities/heroes_changelist.html"
  def get_urls(self):
    urls = super().get_urls()
    my_urls = [
      ...
      path('import-csv/', self.import_csv),
    ]
    return my_urls + urls
  def import_csv(self, request):
    if request.method == "POST":
      csv_file = request.FILES["csv_file"]
      reader = csv.reader(csv_file)
      # Create Hero objects from passed in data
      # ...
      self.message_user(request, "Your csv file has been imported")
      return redirect("..")
    form = CsvImportForm()
    payload = {"form": form}
    return render(
      request, "admin/csv_form.html", payload
    )

{% extends 'admin/change_list.html' %}
{% block object-tools %}
  <a href="import-csv/" rel="external nofollow" >Import CSV</a>
  <br />
  {{ block.super }}
{% endblock %}

{% extends 'admin/base.html' %}
{% block content %}
  <div>
    <form action="." method="POST" enctype="multipart/form-data">
      {{ form.as_p }}
      {% csrf_token %}
        <button type="submit">Upload CSV</button>
    </form>
  </div>
  <br />
{% endblock %}