Board Thread:Questions and Answers/@comment-5788861-20121206194803/@comment-5319459-20121206210446

You need to move it into your tekkit "saves" folder.

For Windows go to your %appdata% folder then .techniclauncher/tekkit/saves/

For Linux go to /home/.techniclauncher/tekkit/saves/

For OSX go to /Library/Application Support/techniclauncher/tekkit/saves/

It will then show in your worlds list, when you open tekkit.