We highly recommend using Automatic Updates, please use this method whenever possible.
This is the same as installation process, however you may choose to backup current theme version and then upload the new version:
Step 1 – Login to FTP
Login to your site via FTP and browse to ~/wp-content/themes/ folder.
Step 2 – Backup the theme (optional)
Download current version of the theme, or simply rename it (or move it to another directory).
Step 3 – Delete theme directory
Delete folder named kalium inside ~/wp-content/themes/
Step 4 – Upload newest version of the theme
Extract kalium.zip file and then upload folder kalium to ~/wp-content/themes/ directory. Make sure you have removed or renamed the previous theme version located.
That’s all, new update is installed!