What is your exact problem?
a) do you know how to copy a
String to the clipboard?
b) do you know how to get data from a cell in the table?
c) do you know how to write a MouseListener
Start by solving "a" first, then "b", and then "c". I'm sure you can find examples on the web on how to use the clipboard. You can start by taking a look at the Clipboard API.
Why would clicking on a cause text to be copied to the clipboard. Does this mean that every time you click on a cell the text is copied? Or are you going to have a popup menu with some Actions that allow you to copy text from the cell.