please unzip the package you got from themeforest.net ONE time. You should get a folder which contains PSDs, Docs and another zip file (which is called twicet.zip. This zip file is the right file. Go to your wordpress admin panel and navigate to Appearance > Themes. Then select the twicet.zip file, upload & install it. That’s it. If you want to use ftp please unzip this file too and upload the resulting folder (unzipped files).