How to insert a checkbox in a django form

models.py:

class Settings(models.Model):
    receive_newsletter = models.BooleanField()
    # ...

forms.py:

class SettingsForm(forms.ModelForm):
    receive_newsletter = forms.BooleanField()

    class Meta:
        model = Settings

And if you want to automatically set receive_newsletter to True according to some criteria in your application, you account for that in the forms __init__:

class SettingsForm(forms.ModelForm):

    receive_newsletter = forms.BooleanField()

    def __init__(self):
        if check_something():
            self.fields['receive_newsletter'].initial  = True

    class Meta:
        model = Settings

The boolean form field uses a CheckboxInput widget by default.