The data element type you are referring to will only allow you to store the attached file in the event.
If you want to import data from file that will populate the your data elements in the event, you will either need a script (you will need to map the fields in the file and the fields in the event in order to import data).
You can also try an app called “Data Import Wizard” by HISP Uganda that is available on the App Store in DHIS2.