Did you follow all of the instructions included in the link you provided step by step? Including replacing your items.cfg folder with the one in the downloads? And did you place everything in the right location?
I would suggest going through the YouTube tutorial that's also in the link and check to see you didn't miss a spot.
Also, when you place these things in your FH folders, make sure the game is closed or it might cause a glitch. If you haven't, delete the items.cfg file and paste it again in your game folder, making sure the game is closed.
Another point I should probably point out, just in case.. If you have previously downloaded other seperate items or item packs, then you must not just replace the items.cfg file as the codes for the other items with go away and therefore it may cause a glitch or best case, you just won't be able to select those other items.