Locate your StackCP User from the list and select Options > Edit.
Select all the Packages you would like to access via Master FTP, then select ‘Save Permissions’.
Select Options > Edit again. This time, scroll to the bottom and you'll see the ‘Unlock Master FTP Access’ section. From here, you can enter your own IP address which will enable you to gain access to all site files via a single login.
Select ‘Add’ once you've added your IP address.
You can now use the following details to connect via your FTP client:
Username: StackCP User Email (e.g. firstname.lastname@example.org)