Two situations need to be distinguished:
Logging in with a user name and password: in this case our support team handles any change of login credentials – please contact them.
Logging in with an e-mail and password: follow the instructions below.
You change your login e-mail, password and phone number in the Personal details section. You get there via the menu in the top right corner – click your name (or e-mail/user name) → General settings → Personal details.
You make the change by clicking the pencil icon next to the detail you want to edit.