If you are using Kalium theme (version 2 and newer) then please visit this article Update Kalium theme.
Update using Envato Market plugin
This method is used only if you need to update: Aurum, Oxygen or Calcium and any version before Kalium 2.
If you don’t see this plugin on your WordPress dashboard then you just need to go to Appearance > Install Plugins to Install and Activate this plugin.
This plugin is very easy to use, but if you have difficulties please just read this guide this guide that was made from WP Explorer.
How do I update the premium plugins?
Just go to Appearance > Install Plugins and install the latest version of that plugin.