I figured out how to get this to install, though I am a bit shocked that the creator wouldn't figure this out for users. Simple install and getting it to work shouldn't require paid support.
Anyways on to the how-to.
The plugin zip that you download from the wpress extend site has a zip file inside a zip file, and the automatic installer can't handle it.
So do this:
Step 1: Delete the rsfiles-download-manager folder from your plugins directory if you've already tried to install it.
Step2: Download the RSFiles zip from the wpress extend site to your desktop
Step 3: Unzip the file you downloaded.
Step 4: Go to your wp-admin plugin page, click on add new, and click on the upload button to manually upload the plugin.
Step 5: Inside that file you unzipped is another zip file called rsfiles.zip Upload that zip file and it will install and activate just fine!