Robot login
To change the password for your Robot account (https://robot.hetzner.com), first switch to the "Accounts" interface by clicking on "User account" in the user menu located in the upper right corner. In the "Accounts" interface, you can set a new password under "Administration" -> "Settings" -> "Password".
Webservice login
If you have created a separate login for the Robot webservice, you can change this password on Robot. Click on the user icon in the upper right corner and then on "Settings" and "Webservice and app settings".
Separate admin login
If you have created a separate admin login for your server, you can change the password for this on Robot under "Server" -> tab "Admin login".
Telephone password
If you have created a telephone password for your server, you can change this on Robot under "Server" -> tab "Phone password".