A common issue that can occur with users new to installing WordPress themes is a “Broken theme and/or stylesheets missing” error message being displayed when trying to upload or activate the theme.
This is because the theme download package on ThemeForest includes additional files to the theme such as the documentation, license etc.
To solve this simply unzip the theme package you downloaded from ThemeForest and upload the themename.zip file which is included (with the file being the name of the theme).
upload the themename.zip file which is included in the package