You can make a payment after you finish your application on the Firstbase.io website (www.firstbase.io). Once you log-in in to your Firstbase.io account, you can click on the Pay Now button (see below) at the bottom of your account and pay using any debit/credit card.
We proudly use Stripe to process transactions. We can also issue an invoice via Paypal or Stripe, so please submit a ticket request for an invoice. A Firstbase.io Customer Success team member will followup with an invoice to your email address.