Library items are elements that you want to reuse or update frequently throughout your website.
Drag the selection into the Library category .
Click the New Library Item button at the bottom of the Library category.
Select Modify > Library > Add Object To Library.
Dreamweaver saves each library item as a separate file (with the file extension .lbi) in the Library folder of the site’s local root folder.
If something is selected, it will be placed in the new library item.