You're not missing anything, because this is Apple's fault. With the release of iOS 8.3, Apple has removed access to the areas where you had the option to copy files. The application is working fine, but it's Apple who is responsible for this issue.
However, I recommend you download and use the latest version of iFunBox. There is a beta package that fixes various problems with the file transfer. To access it, use the official page of iFunBox and click the F icon on the upper-right area of the page to reach Facebook.
Download page: http://www.i-funbox.com/en_download.html