Go to https://app.involve.me/payment-accounts, choose between "Test Payment Accounts" and "Live Payment Accounts", click on the “Connect test account" or "Connect account” button and in the dropdown select Stripe. Follow the prompts to connect an existing account or create a new a Stripe account.

You can use the account that is not in live mode to test your payments. See https://stripe.com/docs/testing#cards for a list of test credit cards.

After you have connected your Stripe accounts, you can then use them to take payments in forms by drag & dropping the "Collect Payments" content element in the editor on the Thank You / Outcome pages of a specific project.

From the "Collect Payments" element, select the Payment Model you want to use (“One-time Payments” or “Subscription & Recurring Payments”), then select the appropriate Payment Account.