I wrote this guide because of the new feature @Nuclear Nezz released in the past few weeks, I hope you enjoy.
First: Grab your Library Jar File and place it in the "Libs" folder found in the DreamBot folder found in your user.home directory.
Second: Head over to your script files and create a new file with the name "libs" in your Source folder A.K.A src.
(Note: The file isn't a .txt, it's just a normal file without any prefixes, if you don't know how to create a default file then you shouldn't be scripting )
Third: Edit this file using Notepad or what ever text editing software you prefer, and write in the name of the library with its prefix (Case-Sensitive).
Ex: mysql-connector-java-5.1.48.jar & jmail.jar
Fourth: Build your script Jar File, also as a helpful hint: when building artifacts in IntelliJ, enable "Include in project build" to build artifacts faster with every compile & select JAR > from modules with dependencies and remove the library from compiling with the script on the artifacts interface.
and that's it!
Thank you @Nuclear Nezz for this fantastic and wonderful update.
Credits to Nezz for explaining briefly how to use the new Libs update. It was a comment in a thread that might get lost, so I made a full thread to keep it in full view to people.