Authorize.net issue

How can I get into the API settings on a specific form. It wont let me 

I checked your form and payment integration. It seems that you have setup it correctly.

I would recommend you to test the payment integration now. In order to test the Authorize.net payment tool on Sandbox Mode, you can check and follow this guide:

https://www.jotform.com/help/221-How-to-Test-Authorize-net-Payment-Tool-on-Sandbox-Mode

If you still need help, please elaborate and we will try to help.