How to i edit template files in groupon clone

Wroupon template files exists at

include/template/

Those are files are smarty like html files.

From there you can change layout of  website/ Change language too.
We would not recommend you to edit template from backend(website admin).

Edit them offline using any html editor(just be cautious ) and upload them on include/template/ .

Then goto include/compiled and delete all files in directory(they are compiled files)

You will see changes then.