There are 2 main ways to update your Blaszok theme:
First one will require Envato Toolkit plugin and can be done entirely in Wordpress Dashboard panel.
The second one is good old manual update. This approach will require FTP access to your server. You will also need to download newest Blaszok package from ThemeForest.
Here you will find more detailed informations how to approach both methods.
Since Blaszok version 3.5, you can update all your bundled with theme plugins from WP Dashboard->Appearance->Install Plugins.