You have to be in your corporate group mother when you uploading SIE4-files into your corporate group. Start by going to "Economy" and then "Data Management" in the left menu and make sure you are in Group Mother mode when uploading a SIE4-file. Under the heading "Economy" you will see what position you are in.
If you are in the Corporate Group mode and want to switch to the group mother, click on the "Show group mother" button.
Then click on "Upload SIE4-file".
Here you upload your SIE4-files by click or drag and drop files in the box.