Click File and "Add file to Library" or "Add folder to Library."
Select the file(s) you want to add to your iTunes music library and double-click or press "Open."
Click on the first imported file in your library, press "Shift" and click the last imported file to select all of the imported files.
Right-click and click "Get Info" in the context menu.
Click the "Options" tab. Click the drop-down menu next to "Media Kind" and select "Audiobook."
Click the drop down menu next to "Remember Position" and select "Yes."
Click the "Info" tab and enter any pertinent information into the empty fields. Click "OK."