Login into FactuurSturen.nl and go to "Settings" > "Connections"
Click at the bottom of the page on "Create API key"
Enter "RCUR" as description and click on add. (make sure that active is checked)
Go back to RCUR and go to "Settings" > "Integrations"
Choose for the invoice app "FactuurSturen.nl"
Enter your WeFact username and the FactuurSturen.nl API key
Your account is now connected and the invoice features are activated