Do you know how to create a menu with items? If not, please read
How to use Menus.
Ok, now you know how to create a menu with items

Now let's get to the actions behind the menu items. The first thing we need is a definition of what you want to copy and paste. Is it text? If so, where does it come from? JTextComponent, the base class of (nearly) all Swing text components, has methods copy(), cut() and paste() that you can call.