EDIT** Johney89 here, i am going to try to attempt to fix the wikis on these mods! i hope i can help by doing this!
The cargo manager is a block that allows passing carts to load and unload items in the Steve's Carts 2 mod. In order to use the cargo manager an Advanced Detector Rail needs to be placed directly beside the cargo manager.
The GUI can be a bit confusing, but it is quite simple. On each side of the block, there is a colored square that corresponds to a section of the same corner in the interface. By clicking the large arrow, you can tell the cargo manager to unload the cart, or load the cart.
Additionally, you can specify from which slot in the cart the cargo manager loads and/or unloads from, such as the railer, or the torch placer. Finally, you can change the color of each side by clicking on the button below the main interface. And for "Undoing" the last Cklick just rightcklick again.