Open an Atom window and add a project folder. There you go. You can create whatever files you want. Atom will not do anything for you or hold your hand, because Atom is not a Java-specific editor and it doesn’t have any opinions about what files you should create or how you should structure your files. That’s all up to you.
Compile and Run a Project
Atom has no awareness of code aside from its own JavaScript and CoffeeScript. It doesn’t matter which package you download, but you need a package that knows how to use the command line program javac. script and atom-runner are the most popular, but there might be others. For my money, it’s worth knowing how to use the command line and then automating everything with process-palette so that you don’t have to use the command line but still have absolute control over your pipeline.
Debug and Breakpoints
I don’t see any packages specifically for debugging Java, but I assume the compiler has that functionality built in.