Itemsadder:
1.Drag and drop the data folder from Itemsadder folder, MERGE any ItemsAdder/data/resource_pack/assets/minecraft/models/item 
MANUALLY BEFORE OVERWRITING in case you have matching items
2.Put your .bbmodel files inside the blueprints folder located at: plugins/ModelEngine/blueprints
3.Now reload the plugin using /meg reload
4.Copy this folder: plugins/ModelEngine/resourcepack/assets/modelengine
And put it into your current itemsadder Resource pack here: ItemsAdder/data/resource_pack/assets/modelengine
5.Then copy over the plugins/ModelEngine/resourcepack/assets/minecraft/models/item/leather_horse_armor.json file
And put it into your current Resource Pack here: ItemsAdder/data/resource_pack/assets/minecraft/models/item/leather_horse_armor.json
6. /iazip

Non-itemsadder
1.Drag and drop assets folder from nonitemsadder resourcepack, MERGE any minecraft/models/item MANUALLY BEFORE OVERWRITING 
in case you have matching items
2.Put your .bbmodel files inside the blueprints folder located at: plugins/ModelEngine/blueprints
3.Now reload the plugin using /meg reload
4.Copy this folder: plugins/ModelEngine/resourcepack/assets/modelengine
And put it into your current Resource pack here: YourPack/assets/modelengine
5.Then copy over the plugins/ModelEngine/resourcepack/assets/minecraft/models/item/leather_horse_armor.json file
And put it into your current Resource Pack here: YourPack/assets/minecraft/models/item/leather_horse_armor.json
6. All done!



to get the modelled items in vanilla game

/give @p bow{CustomModelData:10101}

the CustomModelData will always start with 10101
and the end is when you receive the item with the same model
with the previous number.

Here's the list of items that's possibly has in packs:
iron_sword // for melee weapons(e.g.Sword,Spear)
bow // for bows
shield // for shields
fishing_rod // for fishing rods
crossbow // for crossbows
paper // for cosmetics(e.g.Hat,Wings)
pickaxe // for pickaxes
axe // for axes
shovel // for shovels
hoe // for hoes
