As Zar said, the read me should explain everything. But here is some help:
So, unzip the item pack and take a look at the read me.
If that is no help, follow these.
1. Unzip the item pack
2. Take the items.cfg and extract it to the main FeralHeart folder.
3. Once thats done and the other items.cfg replaced, you need to take the items pack, and copy and paste everything into FeralHeart-->Media-->Items
(I think) that should work.