Go to https://myaccount.microsoft.com/ and login with your Penn West account.
Click "Change Password."
Enter your old password and create a new password (enter it twice) and then click "Submit." Make sure your new password meets all the criteria.
After clicking "Submit," you will be prompted to login by entering your new password.
Reminder: Make sure you update each of your devices that use your PennWest account with your new password!