After creating a new equipment item (using Add new... or Duplicate menus), the newly created item will be assigned with default properties (for example, lens manufacturer, model, maximum aperture, focal lengths for lens item). You can add new properties to the item from all equipment categories (3). This makes sense for fixed-lens cameras, for example. Edit the item properties and press OK to save.
Your equipment is stored in the library file (AnalogExif.ael by default). You can create a new equipment library by selecting Edit->Equipment...->New library from the main menu. To open the equipment library use Edit->Equipment...->Open library menu.