Please use the following guide, it's very easy:
1.) First, the file needs to be uploaded to your file storage ("Files" => "Upload files").
2.) Next, please open a page in the editor ("Pages" => "Manage pages") and select the page, in which you want to include your download.
3.) Click on the button "Insert Link" above the editor and select "Download" in the field "Link type".
4.) Now choose the desired download from your file storage and confirm by clicking on the "OK" button.