Subdomains allows users to setup there main categories as subdomains. It's a lite and fast code.
You can install Subdomains directly from the WordPress admin panel.
Visit the Plugins > Add New and search for 'Subdomains'. Click to install. Once installed, activate, setup wildcard subdomain and it is functional. Finally to choose which categories should be a subdomains goto Settings > Subdomain Settings
Manual Installation Subdomains plugin:
Download and unzip the file Upload the full extracted folder to the /wp-content/plugins/ directory Activate the plugin through the 'Plugins' menu in WordPress and setup wildcard subdomain.
Please check FAQ to wildcard subdomain setup step.
You're done! The Plugin ready to use according to the directions in the description.