You have to define the stats in a text file in Public/Shared/Stats/Generated/Data and define a link to the root template in ...Stats/Generated/Links. I've added several items in Scales and you can reference that if you want to see how I've done some things. You don't have to use an existing text file in there, so you can just add your own. To get a fresh version of all the existing stats, you'll have to extract the Main/MainLSF.paks, but I think LSTools needs to be updated before you can do that. You'll have to use a UUID generator to make a new UUID for the link (I'm not sure if this link can be in the same file as the stat data, or if it needs to be in the link folder.)
Example stats (Peter Lee's Sword):
new entry "WPN_Sword_Kickstarter_Japanese"
type "Weapon"
using "_Swords"
data "Act part" "5"
data "Requirements" "Strength 7"
data "Damage" "4"
data "Damage Range" "1"
data "DamageBoost" "-15"
data "Durability" "10"
data "Value" "9"
data "Weight" "1000"
data "Movement" "1"
data "Initiative" "2"
data "SpeedBoost" "1"
data "ComboCategory" "Sword"
data "Flags" "Unbreakable"
I ought to make a video going through all the stats stuff. A lot of stuff to learn there, and I've picked up some tricks people would find useful I think. For example, note that most of those stats, like damage and value, are level-mapped so they correspond with the level of the item, and others aren't, like initiative, which is a straight value (I think).
Not sure what you mean by how they handle generic rings and amulets. They're in the Loot.lsb I think.