Under Account you will find:
- Password - change it any time. You need the current password to set a new one.
- Security - two-factor authentication. Once enabled, signing in asks for a six-digit code from your authenticator app on top of the password. If someone learns your password, they still cannot get in.
- Contacts - additional people (a colleague, your developer) allowed on the account, with their own details.
Use a password you use nowhere else, and turn on two-factor - it is the single most effective thing on this page.