Storealerttext command is used to store text from the alert popup in a variable defined in parameters .
Select STOREALERTTEXT command from the action drop-down. Leave Screen name, Element key as blank and give a variable name in the parameter section where text from the popup will be stored as shown below:
After completing this step, the test step will look as below:
once data (text from the popup) is stored in the variable, it can be used in the same way as a local variable is used.