Haven't been able to locate a user guide for the multi-unit charger. However, it is pretty much plug-in-n-play. It can charge a battery inside a radio, or also accommodate a battery alone in each of 6 cups. As for replacement parts, they are not available, and you cannot purchase the multi-unit tray separate from the power supply. This is a slow rate charger and would take 10 hours to charge your batteries (or overnight). Radios/batteries should only be placed on the charger when nearly depleted. (Consider your charge a place your radios go to bed overnight.)
If you are having difficulty with charging, clean your battery contacts on the exterior of the radio and inside the charger cups with a pencil eraser.
This tray can act as a radio cloning station. See page 23 about cloning in the XTN radio user guide: http://www.123radios.com/manuals/xtnmanual.pdf