Twitter offers per application keys named Consumer Key and Consumer Secret. To enable Twitter these two keys are needed. Further documentation at Twitter development resources:
Register a new application at Twitter App Creation,
mark the Yes, use Twitter for login checkbox, and
fill Consumer Key and Consumer Secret values:
TWITTER_CONSUMER_KEY
TWITTER_CONSUMER_SECRET
You need to specify an URL callback or the application will be marked as Client type instead of the Browser. Almost any dummy value will work if you plan some test.