Haha, I posted a ticket on Anki about this and they replied :)
Here’s a step by step for anyone with the same problem:
1. Open Anki (I’m using 2.0.8 for Mac OS 10.7.5)
2. Select Browse
3. Select the deck you’re moving cards FROM
4. Select all the cards within the deck (shift click)
5. Once all the cards are highlighted, click Change Deck (it’ll be right above)
6. Select the master deck you want to move the cards TO
7. Click Move Cards
8. Voila! When you open the master deck, you’ll see all the new cards have been inputted.
Made a PDF with detailed screenshots but I can’t attach it here. Emailing it to TextFugu staff — hope it’ll help when you update your Anki import instructions :)