First I tried to find and download Mobo Player on the Vox and finally gave up in frustration. Every download site I Googled had strings attached, like requiring registration or a password or popups obscuring the page and each download link led to another link or some other app they wanted to foist off on me.
Next, I found
jefftheworld's Best App Package on this forum and got the zipped package containing VLC, which I installed via Dropbox.
I then found where to download Mobo Player with my PC and installed that app via Dropbox.
Both players play videos the same way and can adjust the screen size and aspect ratio, but I liked Mobo Player better because VLC would tend to crash frequently and had no means of browsing for video files. Mobo also seemed smoother, sharper and louder. Both would pop up as choices (along with Gallery, which won't play many videos) when I found a video file by browsing with ES File Explorer. Neither automatically searched the Vox for files like Gallery does. So to sum up, I'd recommend Mobo Player because it works better and has its own file explorer.