How do I get my PayPal Checkout payment option to work?

I am testing my form and the payment option is not working. I am getting the "Payment error: client authentication failed" message. Please see the screen shot.

Also, how to I ensure that attendees come back to their forms after making the payment with PayPal? I want them to come back to their completed forms, sign the form, and submit. I cannot see where in the settings of the payment portion I can specify this.

Thank you!

The issue is most likely related to the PayPal details specified in the integration. Please update the PayPal details within the payment field.

Make sure that both the Client ID and the Client Secret are correct. Click on the Continue button to save the changes.

You can get the Client ID and Secret at https://developer.paypal.com/, please follow the next guide for instructions:

How to integrate PayPal Checkout with your form

You were quite helpful. Your info about the Client ID helped a lot. I
wasn't quite sure what that was and I was simply using my username and
password. I was able to locate the appropriate info and it works perfectly
now.
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