The step I was missing was Find/Assert Element. I chose to use the XPath option and used a Chrome addon called “Xpath Helper”.
Using this you can find out the xpath for the element you need to
Then this is stored as a variable for which you can reference in future actions, in my case typing an email address
I am not familiar with ATS, but this sounds like you are testing an external part. It sounds not very strange if ATS is unable to fill input fields outside the scope.
A possible solution would be to mock the services. In that case you use a ‘fake SSO’ which can act locally.