Check if the server has the "GMP PHP extension", if not you or a server admin must install it
Copy the extension to phpBB/ext/DigiByte/digiid
Go to "ACP" > "Customise" > "Extensions" and enable the "Digi-ID" extension.
Go to "ACP" > "Extensions" > "Digi-ID Module" and enable Digi-ID.
Users may set DigiByte address in "UCP" > "MY DIGI-ID" > scan qr code with a Digi-ID enabled wallet.