Hi,
You really make it difficult for us..
The true partname is: TOP264-EG... so it is hard for us to find the datasheet.
Then once you open the datasheet you see the device comes in different packages... some for PCB as heatsink, some for extra heatsink.
On the first page you see a short package description "Advanced package options" It gives a brief information about heatsink options.
Additionally you find a section called "Heat sinking"
....and a PCB example design for each package, where you clearely can see the described copper areas / heatsinking methods.
What more information do you need?
Klaus