It's a bold move from the old HTTP auth to only OAuth. Since twitter is
going to drop http auth in next 10 days, and identi.ca has an OAuth
service provider, it seems dropping HTTP auth support from bti isn't
that bad.
You need to add your consumer key, and secret in ~/.bti:
consumer_key=yourkey
consumer_secret=yoursecret
bti will help you to get your "access token key", and "access token
secret". Put them in your ~/.bti and you're ready to go.