If you mis-click or otherwise mess up a test case, you can click that step and hit Del to delete the step in a test case.

You can also click-and-drag steps around so that they are correct.

In addition, you can manually add test cases with the Command, Target, Value fields if you know the commands (documentation can be found at the Selenium website).

From the File menu, save each test case as needed, and then save the test suite as well so that the entire suite can be accessed again later.

You can also use another tool, Katalon Studio, that can be used on top of Selenium to create test suites.