The process of updating the database is pretty simple. Start the application, connect to the Internet (preferably through WiFi) and then tap on Update virus DB button on the main interface. A new page will open and then tap again on the same button with the same name. This operation will force the antivirus to perform an update check. If it finds any, it should download it to your mobile.
Additionally, access the website to find a visual guide of what I've explained above.