I can make a successful payment using the square payment form example, and getting the payment-processing page with a reply of the transaction details using the Transacrion API. Once this completed Can I see this anywhere on my square account? Like a list of successful transaction in the sandbox?
Sandbox transactions are not visible in your Square Dashboard. The way to view sandbox transactions is to call the ListTransactions endpoint with your sandbox credentials to get a sandbox transaction report. Only live transactions will be visible on your Square Dashboard.