Where should the main processing file be located, and should it have a specific syntax to start with?
You need a sketch file and a entry point (main() method having PApplet.main()) – they can both be included in the same file, and the file(s) can be located anywhere within your project. The main method I use generally looks like this.
public static void main(String[] args) {
PApplet.main(MySketch.class);
}
Where should the tag be embedded?
What do you mean by “tag”?