1. In any top-level folder of your Project View, create a folder named snippets (if not already);
2. Unzip content of snippets_here folder to the 'snippets' folder;
3. Restart Aptana;
4. Activate Snippets View (Window -> View -> Snippets);
5. Find a Drupal 6 folder in Snippets View;

6. Enjoy!
For more information on how to deal with snippets in Aptana go here: http://www.aptana.com/docs/index.php/Adding_a_new_Snippet