1. To get items, you must download them from the forum's Mods and addons section, and save them to desktop. Then, you will see two different files in there, one will be a folder and the other file which is called a .cfg.
Export the .cfg to C: > Feralheart and it will ask if you want to replace or not . Click replace. Next, export the folder's CONTENTS. (Not the folder it's self) to C: >>> Feralheart >> media > items and click replace. Volia, your items should work.
2. Yes, as long as they have a item pack. If they have the same item pack, you will see their items correctly, but if they have a different one, you will still see items, just it may look weird.
Derp I type slow >.>
http://www.youtube.com/watch?v=ikJGMHOR2G8 (http://www.youtube.com/watch?v=ikJGMHOR2G8)
If this is your first time getting items, here is a visual tutorial on how to input your items in game.
1) You get items from peoples item packs such as Delays & Ringos pack, or Theirry's
You can also get the recent up to date item pack which is Pawesome pack 4
NOTE: Different items packs can be visual different for other people. Since some item packs are not related with each other some items can get mixed up and people might see something else. Like if you get the Pawesom pack and a person with Thierrys item pack sees you, they will see something else.
2) As long as people have the same item pack as you then they should see you. For people who do not have any item pack or the same as yours will not see any additional items besides the Christmas hat