Enter the Trigger URL for the test that you want to run on this build step. To obtain the Trigger URL for a test, from the list of Runscope API tests, select the desired test. Next, click on Settings on the left navigation pane. On the test settings, locate and copy the Trigger URL and then paste into this field.
If you need to pass any Custom Initial Variables (i.e. baseUrl=https://yourapihere.com&apiKey=abc123) or Reserved Trigger URL Parameters (i.e. runscope_region=eu2), append those to the end of your Trigger URL (followed by a quetion mark) as query string parameters. The full documentation for Trigger URLs can be found here.