You will need to just ftp the files directly to the server directory. WordPress does not allow you to upload the theme file directly through the WP Admin panel if you have the theme already installed. Pls follow the procedure described here for uploading new themes through ftp or cPanel.
I generally rename the old enticing directory to enticing-backup or something before uploading the new files to directory enticing. This way you preserve the file changes done, if any. And, if something goes wrong or some files go missing, I have the old version to revert or refer to. Hope this helps. Meanwhile, ThemeForest is also working on a mechanism to auto-update the themes in the marketplace.