The Stripe ACH gateway only supports tokenized integration. To use a customer's ACH payment method, you must first validate it directly in Stripe using the "micro-deposit" function. See the Stripe documentation for more information on how to do this. Once you have completed the validation process, you can enter the customer's token information into the Payment Method section of their customer record.
To add a customer's payment method information to Stripe through the dashboard, see the Stripe documentation.
Fusebill will require Verified IDs for the bank account (starting with ba_) and customer (cus_) available in the customer page in Stripe.