You haven't imported the data file. Your variables will be listed here after the dataset is imported.
Descriptive Analysis and Data Visualization
Conduct descriptive analyses for all variables in a dataset simultaneously in three steps:
Import the dataset.
Select variables and verify their type.
Click Univariate or Bivariate and enjoy the results.
Click this button to import the dataset saved in a comma separated value (CSV) format. If you have an Excel file, save it into a CSV file before importing.