To change the coversheet text, go to 'File...Options...Configure System' then click on 'Coversheet text' in the 'Reports' section.
The text that is used across all matters is displayed and can be edited as needed.
NB : The coversheet text is designed to be a standard output across all matters for all users to ensure consistency for your practice. Changing the coversheet text will affect all matters, not just the one you're working on.
In PPv5 you can also add your firm's logo, or any other image, to this coversheet. To do this, go to 'File...Options...Configure System...Reports...Columns & logo'