From their announcement:
Want to win one of 6 free battleforces / battalions? All you have to do is:
1. “Like” their facebook page.
2. “Like” the post.
3. Leave a comment on the post stating which 40k Battleforce or Fantasy Battalion you want.
Winners will be randomly chosen and sent the battleforce or battalion of their choice, as long as it is still available, with FREE shipping.