How do I change my password?
From “My account”, in the security section — you need the current password.
The minimum is eight characters; a long phrase you can remember and nobody can guess is better.
If you signed in with Google you have no password on the platform, and Google remains your way in unless you create one.
If you have forgotten it, use “Forgot password” on the sign-in screen. A link is sent to your registered address and expires after sixty minutes.