Nested in Team Settings are your "Test Settings," where you'll manage default testing budgets, test goals, which ad account you'll be testing out of, and more.
Only Administrators have the ability to change default test settings. Here Admins will be able to set the default settings for all tests, so team members can hit the ground running with testing content.
Pick a goal from any of the drop downs or type in a different default budget. To ensure that your changes save, click the "Update" button at the bottom of the page.