- Copy to your project's vendor/extensions dir, and make sure the naming is right (remove the 'spree-' prefix).
- Reboot (or deploy to) your server.
- Go to the backend of your shop, and go to configuration > paying methods.
- Create a new paying method, and select 'Billing::Ogone' as the provider
- On the next screen, alter the valuta if needed, and fill in the Ogone passphrases and account name. If you have not yet set up your SHA pass phrases: Log in on Ogone, and go to Configuration > Technical information. The SHA-IN can be set under 'Data and origin verification', the SHA-OUT under 'Transaction feedback' You also need to check 'I want to receive transaction feedback parameters on the redirection URLs.' in the Transaction feedback tab.