When you receive a payment request from a group admin, you can pay it in the app on spond.com/login or through the email if you receive notifications by email.
In the app or on spond.com you will see a notification on "payments" at the top of the menu, press this.
The payment request will contain information about what it is for and when it's due. You can also send a message to the admin who has sent the request.
Press "pay" / "go to payment"
Enter the card information if you have not already done so. Read more
Press "pay"
When the payment is completed, you can find the receipt under Payments > Performed payments