By default, your keychain password is the same as your user password (the password you use to log in to the computer).
If the new password does not update your keychain automatically and you encounter pop-up messages informing of you to "enter your keychain password," you will need to reset your default keychain.
Reset Default Keychain
- Click on an empty spot on your desktop to bring up the Finder menu on the top left of your screen.

- Click on the “Go” option and then select “Utilities” from the drop-down menu.

- The Utilities window will open. Locate “Keychain Access” and double click to open it.

- Click on “Keychain Access” in the top left menu. Select “Preferences…” from the drop-down menu.

- The Preferences window will open. Click on “Reset My Default Keychain.”

- Enter the most recent password you use to log into your account and click “OK.”