OK. Yes, you should migrate to the HDD, but in order to use Migration Assistant you first need to install OS X on the drive. Based on what you said you have OS X on the SSD. So what you need to do is put OS X onto the HDD. Here's how you do that:
Clone Lion using Restore Option of Disk Utility
Boot to the Recovery HD:
Restart the computer and after the chime press and hold down the COMMAND and R keys until the menu screen appears. Alternatively, restart the computer and after the chime press and hold down the OPTION key until the boot manager screen appears. Select the Recovery HD and click on the downward pointing arrow button.
1. Select Disk Utility from the main menu then press the Continue
button.
2. Select the destination volume from the left side list.
3. Click on the Restore tab in the DU main window.
4. Check the box labeled Erase destination.
5. Select the destination volume from the left side list and drag it
to the Destination entry field.
6. Select the source volume from the left side list and drag it to
the Source entry field.
7. Double-check you got it right, then click on the Restore button.
Destination means the MacStorage drive. Source means the internal Mac SSD drive.
When you are done you will have a bootable system on the HDD. You now want to boot from the HDD by doing this:
Boot Using OPTION key:
1. Restart the computer.
2. Immediately after the chime press and hold down the "OPTION" key.
3. Release the key when the boot manager appears.
4. Select the disk icon for your MacStorage drive.
5. Click on the arrow button below the icon.
Once this is accomplished you can now use Migration Assistant to restore your Home folder, Applications and support files, and system preferences to MacStorage.
See you later this afternoon.