At the first start you will be asked to enter the confirmation code and password (if two-factor authorization is active).

An example is shown below:

With further launches, this is not required.

An example is shown below:

Telethon (0.15.4.3)  - Full-featured Telegram client library for Python 3
  INSTALLED: 0.11.5
  LATEST:    0.15.4.3
Installation: pip install telethon==0.11.5