From left to right in our image.
Cap - Barrel - Converter - Nib Unit - Feed and Nib.
The convertor holds ink when filling from an ink bottleNib Unit holds the nib and the ink feed.The feed is behind the nib and regulates the ink flowFinally the nib itself.
The nib and feed fit into the nib unit and are compression fit. Never use tools, there is no need for tools and they will mark or distort the components. Use your finger and thumb only.