To disable a user's account:
  1. Start from your Core persona.
  2. Navigate to Users/Access > Profile > Edit User Profile Data.
  3. Search/select the user you want to disable the account for.
  4. Scroll down to Sign In Information, and click Edit in the upper right corner of that channel.
  5. Click the Disabled/Locked check box.
  6. Click Save.

A Platform Manager can go back into the account at any time and unlock the account. 

Disabling/Locking an account does not change or remove any of the user's information from the system. This simply prevents them from logging in.