Q: how to stop this annoying keychain reminders on popping in my screen every minute

Originally, the keychain password is the same as the login password for the account. The login password can be changed in any of three ways:

1. By the user, in the Users & Groups preference pane. In this case, the keychain password is automatically changed to the new login password
2. By the administrator (if different), also in the preference pane. The keychain password is not changed.
3. By anyone who has physical access to the computer, in Recovery mode. The keychain is replaced by a new, empty one with the new password, and the old keychain is saved with the old password.

To change a keychain password, launch the Keychain Access application and select the keychain from the list on the left. If the list isn't showing, select

          View ▹ Show Keychains

from the menu bar, or press the key combination command-K. Then select

          Edit ▹ Change Password for Keychain...

You must know the old password in order to set a new one. Otherwise you'll have to reset the keychain.