UML representation of my project

I am learning to code with java and have been using bluej up until recently being advised to upgrade to something like intellij.

I like intellij so far but I am confused as to how to represent my project in UML format as Bluej does by default to show me subclass relations, interfaces etc.

I downloaded a SimplyUML plugin but when I right click on the package file and add it nothing happens so not sure what I am doing wrong.

Is there a simple way to do this?