ATMA V is fun and easy to use. Start by downloading and installing ATMA.

ATMA opens to display the main window, with a Character/Item View Control Bar on the left, the Info Bar on the bottom, and the Item Property View and Dupe Detector open. These can all be turned off by clicking the small "X" in the upper right corner. You can display them again by selecting them in the "View" menu. The Tool Bar at the top and the Status Bar at the bottom can also be turned on/off here.

The File menu has many options for loading both characters and items. You can load a character file (.d2s), ATMA stash file (.d2x), item file (.d2i) or an entire directory of files. Manipulating items is easy, simply drag and drop to move the item to and from a character window, item view window or a stash.