I made a thread about this a while ago, it's probably only a few pages back.
To spare you the time, I'll just tell you how to do it.
Make a backup of your troops.txt and item_kinds1.txt files.
Open Phantasy Calradia in morgh's editor.
Edit the troop.txt and items_kinds1.txt files in morgh's, not your backups though.
Hold the down arrow, once an error pops up, hit update troop, or update item, and then keep going down through the item/troop list until you reach the bottom.
Once this is done, save your changes, open up TweakMB, then once you're done with your changes, simply put your backups back in.
If you don't put your backups back in, then all of the skills that this mod adds, and all of the special items, may be broken.