1. Please download the file clustalw-2.1-macosx.zip from here. 2. Double-click the downloaded clustalw-2.1-macosx.zip to generate the clustalw-2.1-macosx folder. 3. Select [File]→[Parallel Editor]. 4. Click the [Import Sequence] button and read sequence files. 5. Click the [ClustalW] button. 6. Set the path of the ClustalW you just unpacked to 'Select ClustalW' in the ClustalW Parameter 7. If you want to use the ClustalW2 , select the 'clustalw2'.