Account
Changing your password
Open Settings → Sign in, enter your current password and the one you want, and confirm.
A new password needs all four of these:
ten characters or more
an uppercase letter
a lowercase letter
one character that is not a letter — a digit, a symbol or a space
The rule applies when you set a password, never when you use one. A password you have had for years goes on working exactly as it did.
If you cannot get in to change it, ask for a sign-in link instead.