Configure external payment action - woudt/bunq2ifttt GitHub Wiki
Configure external payments - strongly advised against!
Warning: it is very dangerous to enable external payments. There are many ways you can loose all your money!
Please consider using Draft payments instead. That way you create a payment that simply needs to be approved in the bunq app. For draft payments you only need to supply OAuth authorization in your app, which is a lot safer than the full access API key that is required for external payments. See Security.
It is so dangerous, that external payments are disabled by default. You can enable them with a small source code change, that isn't hard to find, but for which no instructions will be posted here.
The configuration is similar to Configure draft payment action, see the screenshot