To open an existing design:
Click Open Existing Design or in the File menu, select Open. This displays the Open dialog box.
Select File. Type the full path name of the .adb file in the File Name box, or select the file from the list.
Click Open. The Designer custom design flow window appears and all tools and commands are activated. When you open an existing design, Designer checks to see if you have modified your netlist since the last time you imported the netlist into this design. If you have, Designer prompts you to re-import your netlist.