Article: You'll need to have a second account with administrator privileges enabled on your computer, and you'll also need to know its admin password. If you're logged in on your account, log off and then select the other admin account. This will open the system settings. All of the users on your computer will be displayed. This will allow you to make changes to the Users & Groups settings. You'll be prompted for the admin password for the account you're using again. You'll find this listed in the menu on the left. You'll see your account settings appear. This will allow you to create a new password for the account. You'll need to enter the password twice to confirm it. Click "Change Password" to save it. You'll be able to log in using the password you just created. When you log in with your new password, you'll be prompted to update your Keychain password or create a new one. You won't be able to update the password since you don't know the old one. You'll need to create a new Keychain that you'll using moving forward.
What is a summary of what this article is about?
Log in with the secondary admin account. Click the Apple menu and select "System Preferences." Select "Users & Groups." Click the padlock at the bottom of the window. Select your original account. Click the "Reset Password" button. Create a new admin password for your original account. Log out and log in with your original account and new password. Create a new Keychain.