To open the Uploader select a file on a 'File List', open the 'File Menu', right-click on the file and select the 'Upload' option on the popup menu, or press <Ctrl+U>.

You can select any file at any time and upload it.

All you'll be asked is in which server directory you want the file uploaded to.

If you haven't configured the 'FTP Client' then you'll have to do so before starting the upload and it will automatically be shown to you.

It's a one-two step and you can upload files regardless of their sizes.