How do I input HTML into the help text of a Django form field?

You can use mark_safe in the model to indicate the html is safe and it should be interpreted as such:

from django.utils.safestring import mark_safe

i_agree = forms.CharField(label="", help_text=mark_safe("Initial to affirm that you agree to the <a href="https://stackoverflow.com/contract.pdf">contract</a>."), required=True, max_length="4")