Adding packages to Mcreator projects???

Hello,

    I have a .jar file that sits in my 'downloads' folder, and am wondering what directory (in my MCreator project) do I need to 'cut and paste' my .jar file into, in order to eliminate all the errors in my .java code from lines that try to 'import' interfaces (such as org.bukkit.*) from my .jar file. The error I am getting is, "package org.bukkit.* does not exist.". Thank you.