If you know your current password and want to change it:
Click on Manage Account Security > Reset Password.
From Client Portal, click on your avatar (Desktop - top right), or hamburger icon (bottom left) then three dots on the top right (for mobile apps) > Settings
Under settings, click on Manage My Account
This will open "My Account", which takes you back to the first point.
If you don't remember your password:
Go to https://account.createmusicgroup.com/ or https://portal.create.tv/ and make sure you're signed out
Click on "Forgot your password?" and follow the steps.