Go to the campaign page, and under Payment account, click on the account added.
You will see the option to "Allow donor to cover charges" in the payment account section of your campaign page settings.
You won't be able to turn it ON if the Fixed and Percentage charges associated with the payment gateway are not set.
Click on Go to settings, and input the Fixed charge and Percentage charge associate with the payment gateway, and click on Save.
It is advised not to check on the Recalibrate box, as it could change all the previous gifts received.
How does the payment page look to the Donor once the setup is done?
Reach out to us at firstname.lastname@example.org in case of any queries.