Effective Tuesday 3rd of October 2017 the IDEAL module is no longer maintained and as a result this module will no longer be distributed with the WHMCS software. Please consider IDEALMollie as an alternative.
To activate the iDEAL module in WHMCS, navigate to Setup > Payments > Payment Gateways and choose iDEAL from the Available Gateways dropdown. Then complete the fields that appear using details from the iDEAL control panel.
The certifcate related files (.cer and .pem) can be uploaded anywhere, we recommend above the public_html directory of your site, and then enter the path to those files in the Private Key and Private Cert fields.
Certificate files can be created using OpenSSL. Instructions can be found in your Ideal Postbank/ING Manual
Do not forget to also upload your cert.cer file to your Postbank/ING Ideal Dashboard!