Codex text
PC version...
To equip new weapons, armor, and accessories, double-click or drag-and-drop the item. Right-clicking an item moves it to the Junk category to be quickly sold at stores. Drag an item to the edge of the screen to destroy it.
Xbox 360 version...
Equip new weapons, armor, and accessories for each of your party members. Move items to Junk to sell them quickly in stores. Use left trigger and right trigger to cycle item categories.
Inspecting items will show you detailed statistics. The stars next to an item indicate its power relative to your level.