I'm sorry to say, but you need some kind of 3rd party device if you odn't want to use the GTS hack. If you don't get a USB backup device (described at the bottom of this post: http://projectpokemon.org/forums/showthread.php?16601-How-to-Backup-Restore-your-retail-cartridge-save-file-(D-P-Pt-HG-SS-B-W-Nearly-any-other-DS-game)), or an Action Replay (unless you use a 3DS, then it won't work), then this will not even be possible.
If you get a USB backup device (I have the NDS Backup Adapter, but the SMS4 is also a good choice), then you will want to find the liberty pass PGF, and use the Mystery Gift Editor to add it.
If you get an Action Replay, use the Mystery Gift Editor to create an Action Replay code.
If you need more help, let me know!