VerifyUnChecked
VerifyUnChecked command is used to verify if the checkbox represented by the Locator(Page and Element) is unchecked .
Select VERIFYUNCHECKED command from the action drop down, select desired Screen name, Element key and leave the parameter section blank as shown below:

After completing this step, test step will look as below:

If checkbox is found unchecked then this test step will pass else this will fail.