1. In the Library module with photos selected in the Grid view, or with a selected photo in Loupe, Compare, or Survey view, choose Library > Rename Photos.
2. In the Rename Photos dialog box, choose an option from the File Naming menu. Choose Edit if you want to specify a naming option using the Filename Template Editor. See The Filename Template Editor and Text Template Editor.
If you specify “sequence” for a naming option, Lightroom numbers the photos sequentially. If you don’t want the numbering to begin with “1,” type a starting number in the Start Number text box.