WordPress - alternative update
Update on admin panel
Go to your Plugins list and deactivate and delete your current Smart Slider 3 installation. Don't worry, your sliders will stay!
Go to your Plugins → Add new → Upload Plugin and browse the smartslider3-wordpress-3.x.x.zip.
Press Install Now, and if the installation was successful, click on Activate Plugin.
Now you will see the Smart Slider 3 Pro plugin appearing in your plugins list. After activating it, you will see the Smart Slider menupoint appearing in your left WordPress menu.
If the installation wasn't successful, try out the Update through ftp method instead.
Update through ftp
Unzip it into your computer.
Upload the unzipped nextend-smart-slider3-pro folder to your website's ftp, to the wp-content\plugins\ folder.
Go back to your backend, and activate the Nextend Smart Slider 3 Pro plugin.
The cache should automatically refresh, but if you see some problems, press that Clear cache button!