open my Imac password

Perhaps this may help: https://support.apple.com/guide/mac-help/reset-your-mac-login-password-mh35902/mac

Keep in mind that if you proceed, this will reset the Keychain, and you will also lose any saved passwords or certificates.

If you are locked out of your Apple ID account you can go to https://iforgot.apple.com

This will provide you with the recovery steps you put in place for this situation.

Here are some support articles that should help:

If you forgot your Apple ID password - Apple Support

If you forgot the answers to your Apple ID security questions - Apple Support

If your Apple ID has been locked or disabled – Apple Support

Restart in the Recovery Partition ( hold down Command + R on startup) and then locate the Terminal app. In Terminal type resetpassword and follow the on-screen directions.