Change the login password on Mac

1. On your Mac, choose Apple menu  > System Settings, then click Users & Groups  in the sidebar. (You may need to scroll down.)

   If you’ve forgotten your login password and can’t log in to your Mac, see the Apple Support article If you forgot your Mac login password.

2. Click  next to your user name.

3. Click Change.

4. Enter your current password in the Old Password field.

5. Enter your new password in the New Password field, then enter it again in the Verify field.

6. Enter a hint to help you remember the password.

   The hint appears if you enter the wrong password three consecutive times, or if you click the question mark in the password field in the login window.

7. Click Change Password.

Source: Change the login password on Mac - Apple Support