Download the data2ext flashable zip from the first post on this XDA thread: Link.
Put the data2ext flashble .zip on the SD card.
Flash the zip using the ClockworkMod Recovery.
These next steps will ERASE EVERYTHING on your SDCARD! Backup now, then come back to this step.
In the ClockworkMod Recovery, select Advanced and then Partition SD Card.
Depending on the size of the SD card, pick the size of the EXT partition (1024 MB is the recommended MAX).
Swap isn't needed for data2ext, just keep it at 0
Reboot the phone.
Launch the Terminal Emulator (or use ADB (adb shell)) & type the following commands:
su
Ensure that mmcblk0p2 isn't mounted anywhere. You can do this by running mount|egrep mmcblk0p2. If that returns anything, the ext partition is mounted, please unmount it using this command in Terminal Emulator: umount /sd-ext or umount /dev/block/mmcblk0p2
mke2fs -m0 -b4096 /dev/block/mmcblk0p2
tune2fs -O extents,uninit_bg,dir_index /dev/block/mmcblk0p2
e2fsck -yf /dev/block/mmcblk0p2
tune2fs -o journal_data_writeback /dev/block/mmcblk0p2
tune2fs -O ^has_journal /dev/block/mmcblk0p2
data2ext --enable
Reboot your phone however you would like, assuming no errors from the above commands.
Once the phone finished rebooting, data2ext should be setup at this point. You can check by looking at your free space under Settings | Storage in Android. It should be close to what size you chose in step 6, but will depend on how many apps you have installed.
Restore data to sdcard (if any was backed up)