In the Odoo dashboard

From your Odoo space, click on Configuration, then on Payment intermediary
Find and click on Fintecture
Click on Edit at the top of the page
Copy the App ID previously generated from your Fintecture space and paste it in the corresponding field
Copy the App Secret previously generated from your Fintecture space and paste it into the corresponding field
Upload the Private Key file previously generated from your Fintecture space into the corresponding field