How can I get access to the Workfront API

Is this what you are looking for?

https://developer.adobe.com/workfront/api-explorer/

This link will provide you with the basics for using the API: https://experienceleague.adobe.com/docs/workfront/using/adobe-workfront-api/api-general-information/api-basics.html?lang=en

I've always just gone into Setup\System\Customer Info and created an API Key. This is the API Key I use to plug into Postman and other API authentication services. 

As noted below the API explorer provides the meat of the documentation and is what you will ultimately bookmark: https://developer.adobe.com/workfront/api-explorer/

Thank you all for your help. I was able to get the API connection working after working with a Workfront Support rep. But now, I hit a new wall that someone might be able to help with. I created a test request, converted it to a project with one of our templates that has a custom form attached to it. When I am in the API, I am not able to see the fields in this custom form, even after I fill them out with data and refresh the API call. The only fields I can see are ones that exist on the default Overview form. Is there something that I am missing? Do I need to add another parameter to my URL to find these fields? Or is it something in the script at the bottom of Postman that I can type in that will search for the fields on my custom form?

I have included pictures below for clarification.

In the section where you see Description, That is the custom form I have associated with the template that I select when I convert the request to a project.

Here is what I am seeing in Postman.

Thank you for your help.