Setting up Plex Media Files Using Stablebit Drivepool

I already asked a similar question about whether using Drivepool for the media files was a good idea, but it brought up a new one.
I'm running Plex on a re-purposed gaming computer, which has run out of space. I set up a Mediasonic ProBox HF2-SU3S2 4 Bay 3.5" SATA HDD Enclosure, connected directly to the server box by eSATA. In the computer, my Plex media files are on a 3TB drive that's full (J:), while Plex, and the Plex Data Folder is staying on a smaller C: drive. The extra storage will come from adding a 4TB drive that will go in the new Mediasonic ProBox (more added later as needed).
After getting it all running, and installed Drivepool, much to my embarrassment, I realized that I didn't know how to set up Drivepool for this use. I now have my old Plex media drive (J:), and the new 4TB drive (K:), making the new virtual drive DrivePool (L:). After reading the instructions over at the Stablebit site, I'm still a bit confused on the best way to set this all up for Plex media use. I thought that what I needed to do was move the media folders from the old J drive to the new pooled virtual drive L, then tell Plex to look on L for the media files. Is that all there is to it? After that is done, what have other users here of Drivepool found was the best way to set up file protection and backups.