Once the 3rd party library has been configured, you can use the Java classes in QIE custom mapping functions. To import an entire package, you can use the following:
importPackage(Packages.com.mycompany.mypackage);
After that, you can access any of the classes contained in the com.mycompany.mypackage Package.
Alternativly, you can access the class directly as follows:
var myClass = new Packages.com.mycompany.mypackage.MyClass();