You just have to use maven or gradle, you can get the API here
GitHub - LoneDev6/API-ItemsAdder: This is the ItemsAdder API repository. It serves as a Maven/Gradle reference for anyone looking to access the API without embedding/owning the entire plugin.
GitHub
Description
ItemsAdder includes an easy to use API for Java developers.
To access it just include dev.lone.itemsadder.api.ItemsAdder in your code.
Important notes
It's very important to listen to the ItemsAdderLoadDataEvent event in order to make sure items are correctly loaded before accessing them.