For starters you might want to read the wiki article about repartitioning of the emmc http://wiki.maemo.org/Repartitioning_the_flash . Although it was written for increased space in optfs, the technique of partitioning, editing system files is essential to get space for an external swap partition.
Try to digest this content, google for some more info, or ask specific questions here in the forum, may be in a separate thread.
I am sure, you will get help along the way.