To install OpenViX download and ftp to a library used by OpenATV to store downloads (HDD/usb) and use flashonline
For openpli download the multiboot version (there are 2 versions for the HD51 - one for multiboot, one for usb flashing) and then ftp to the receiver etc.
In OPenViX, you use the ViX plugin & ImageManager to do all this.