You have to change your Guideline name, ok now it's so easy within a few clicks.
Login to Frontify
Click on the Brand to get to your Guideline
Click on the gear icon
Change the Guideline name
From the Dashboard, click on the Brand to reach the Guideline:
Click the gear icon and change the name of your Guideline
Important: you have to be the owner or editor of the Guideline or an account admin to be able to change its name or background image. Otherwise, the gear icon does not show.