Customize Form for AD Auth when Password Changes

Hi
 
I have an example APM policy in Modern profile, with the Logon Form and AD Auth step:

When a user is required to change their password they are prompted with "The domain password has expired. Please change the password."

I would simply like to replace the text with:

"Please enter your new password. 
Passwords must meet the following requirements:
•    Password must not match a previous password.
•    Password must be at least 12 characters long.
•    Password must contain at least 3 of the following:

    - Uppercase alphabetic characters
    - Lowercase alphabetic characters
    - Numeric characters
    - Non-alphanumeric (special) characters"
I have looked at various F5 references for APM customization and made various changes but I am struggling to work out how to change this. I looked at this reference but it didn't help me APM Advanced Customization Examples with Modern Template, v15.1+ | DevCentral
 
Assistance much appreciated!
Mick