How to download multiple files from
The box app is nice but rather limited, one of those limitations is the inability-to download more than one file at a time to the touchpad. My workaround is to use Gemini file manager. I haven't used internalz file manager to know whether it operates in a similar manner but gemini's two pane view makes it very manageable.
Step 1

Open the Gemini app and tap the network tab, follow the instructions to add After completion close the app and reopen it, tap the network tab and tap the icon. The files will appear in the right pane.

Step 2

In the left pane will be your destination folder use open mode to select your destination (music, video, dcim, etc) then on the pane tap the selection mode icon at the bottom. Now select the files from tapping each sequentially till done, then hit the copy icon and voila! You can then fire up an app and do something else in typical webOS style while your files are downloading.

Additional tip

If you stop using your touchpad before your download is complete, start an app like streaming radio that will prevent the device from going into standby and stopping the download.
Hope this helps, I had a big grin the first time I did it.