Create the existing page over again based on its original Blueprint.
Use the "Regenerate This Page" option in the Brikit Blueprints Menu to create a new page from the source Blueprint. You will be prompted to re-enter any substitution field values. On close of the Blueprint wizard, you will have a new page, populated with your substitution field values.
Note that any existing content on the page will be overwritten by this process.
It is located in the Confluence Header. Check out Accessing the Brikit Blueprints Menu for detailed instructions.
Click 'Regenerate This Page'
Don't see it? That's because the page you are on was not originally generated from a Blueprint. This option is only available to pages created from Blueprints.
Clicking this option takes you through the 'Blueprint Wizard' process, a set of windows with options for entering data needed to generate the page.
Enter in any substitution field values
If there were substitution fields used in the source page Blueprint, then you will be prompted to enter them here.
Change the page title (optional)
This will 'update' the existing page by regenerating it from the source page Blueprint based on your substitution field values.