To add bitmaps to a document at runtime, use the ActionScript™ 2.0 or the ActionScript 3.0 BitmapData command. To do so, specify a linkage identifier for the bitmap. For more information, see Assigning linkage to assets in the library in Learning ActionScript 2.0 in Adobe Flash or Exporting library symbols for ActionScript in Programming ActionScript 3.0.
Select Linkage from the Panel menu in the upper-right corner of the panel.
Right-click (Windows) or Control-click (Macintosh) the bitmap name in the Library panel, and select Properties from the context menu.
If the Linkage properties aren’t visible in the Properties dialog box, click Advanced.