How do migrate and makemigrations work in django

I am new to Django. I have been following this SO solution lately to upload an image to the server side:

Need a minimal Django file upload example

I ran commands makemigrations and migrate, possibly these commands created the sqlite table. Now whenever I do ./manage.py dbshell, and then do .tables. it shows to me rango_document (rango being the name of my application), as one of the tables created.

I wish to alter the table structure and add a few fields for the future DB entires. In which file does django store information about this sqlite database, so that it could be edited and new fields be added?