The file user-config.py should be placed in the folder of your Pywikipedia installation. Add the following text to a text file (using a text editor), replace YOUR BOT'S USERNAME with your bot's actual username, and save as user-config.py:
mylang = 'en' family = 'appropedia' usernames['appropedia']['en'] = u'YOUR BOT'S USERNAME'
If you have an admin/sysop account and want your bot to be able to perform admin actions, add this line at the end of the file:
sysopnames['appropedia']['en'] = 'YOUR ADMIN USERNAME'
and replace YOUR ADMIN USERNAME with your actual username, on your admin account. You will be warned before the bot makes a change requiring admin permissions.