two-stage user activation from database
Always best to include the Drupal version you are making use of, for the purpose of the answer will assume its Drupal 7; 

So there are two parts to this;

1) The user data upload to drupal; you could make use of the Migrate module; I would think in the very least you would need to set the username and a temporary password to facilitate the first time login instance.

2) To force the user to fill in his details you could make use of the hook_user_login in a custom module implementation to validate that the user's details have been filled in.