Make sure to unzip the package that you downloaded from themeforest, Before uploading it to your WordPress installation as a theme. Because, it is not only a theme and contain many other related files & folders like Documentation, Import XML, License Text, PSDs, Theme Files and Theme Zip
When you are ready to install this theme, you must first upload the theme files and then activate the theme itself. The theme files can be uploaded in two ways:
FTP Upload: Using your FTP client, upload the non-zipped theme folder into the /wp-content/themes/ folder on your server.
WordPress Upload: Navigate to Appearance > Themes > Add New > Upload. Go to “Browse/Choose File”, and select the zipped theme file named . Hit “Install Now” and the theme will be uploaded and installed.
Once the theme is uploaded, you need to activate it. Go to Appearance > Themes and activate the uploaded theme.