Using variables, you can choose any element on the screen or in the Object tree and assign a parameter to it. Your parameter is then available throughout the rest of the test and will be set in runtime.
To create the variable, select Use Variable.
Select an element in your test to associate to the variable and select Add Action.
Some apps have dynamic content or content you want to validate based on your test data. For example, validating that the right email is displayed on the profile screen when logging in or registering to the app. To create a validation for your variable, see Assertions and validations.