PayLine
PayLine add-on include translation files for French language. If your website/user is in French, you will see the admin and the front-end already translated to French.
1. Activate PayLine as payment gateway
Once you have activated PayLine plugin, you need to validate the licence in HBook > Licence.
Set PayLine as active payment gateways in HBook > Payment > Active payment gateways.
2. In HBook, add PayLine credentials
You will need to add the following information that is communicated by PayLine in HBook > Payment > PayLine settings.

Which Test cards to use?
You can find the test card details in this help article from PayLine.