Here is an instruction on how to do it - link

1. Create a file in the app folder "utils.py"

2. Insert code

def comma_splitter(tag_string): return [t.strip().lower() for t in tag_string.split(',') if t.strip()]

3. Insert a string into a file "settings.py"

TAGGIT_TAGS_FROM_STRING = 'appname.utils.comma_splitter'