Keychain Password on my MAC

See the article https://support.apple.com/en-in/HT201609

In system preferences > users and groups , tap admin account and click on change password , if you enter the credentials the login password is changed , you can't find out keychain password in keychain access as it is encrypted , perhaps can only change it .

If you had further issues , post the screen shot of pop ups ( make sure you always hide mail address and photo ) before posting .Also clarify are you using 2FA or secondary authentication account .

Normally, your keychain password is your user password unless you have changed the keychain password. You can go to System Preferences/Users & Groups, select your account, and then click change password. Resetting your password there should change the keychain password to your user password. After changing the password, go to the  menu and log out of your account. Then log back in. That should complete the password update.