vx858 is a Rockchip player, you need to convert your video using aviconvertor first, then simply use drop and drop to copy to the player, for mp3's simply just drag and drop on to the player.
If you don't have aviconvertor then you can download it from this site, just rememeber to set the video resolution to 320x240, or you will get the message "file format error" on the player.
__________________
-----------------------------------------------------------------------------------------------------------
|