Rainfall data can be exported from MX Drainage in IDF format using the Scheme > Export > LandXML menu. This creates an XML file, and also a CSV file which contains the rainfall data in IDF format. To use this data in a Storm-Sewer product, go to Components > Storm Data, and create a new User Defined IDF Table. Make sure the units for the Duration column are minutes (right click on the column and click Units and Formatting if they're not). Finally, click the Import icon and browse to the CSV file to import the data. This will import a series of storm events - one for each of the return periods. You can then select the storm event you want to use in the Components > Global Storm Events dialog.