In order to upload a file in the directory of the created site you need, when logged in as an administrator, to click File Manager in the menu. Click the Upload   button. The following dialog box will be displayed:

Click Sfoglia to select the name of the file to upload and click Add.
Select the folder where uploading the file. If you are uploading a .zip file it is possible for you to click the check box in order to decompress the file.
At the end click Upload New File.