Upload max filesize
There was an error loading this file to the server.
The uploaded file exceeds the upload_max_filesize directive in php.ini.
If you can see an error message like this when you are trying to install Smart Slider, that means that your server has a limiation, that files that are larger than the value defined in the php.ini (or .htaccess file) is smaller than the Smart Slider's intallation package. The limitation on most cases is below 2Mb.
If you would have access to your php.ini file, you could modify this value by seaching for the upload_max_filesize or post_max_size words.
If you wouldn't have access to that file, you can still install the slider by connecting to your website via FTP. You can use the Install from Directory method on Joomla, the Upload through ftp method on WordPress, and the way you should install the slider on Magento Manually like this.