I had a bit of trouble with it at first, but it's pretty simple actually... here's what I did to install the pawsome item pack:
1. Download the pack.
2. Go to downloads and open the file
3. Click on the read me (if there is one), and there should be instructions there. Follow them.
3ALT. If there is no Read Me, open the file with the items, cut/copy/drag them to C:>Feral Heart>media>items and paste/place them there. If it asks to replace files, click yes.
4. This probably should have gone higher up in the list, but if you haven't done this already, go to your Feral Heart folder and there should be an items.cfg file. Drag this into items.
Hope this helps!