Drupal’s core caching modules are enabled by default on new installations. If you need to check or enable them, go to the Extend page and make sure Internal Page Cache, Dynamic Page Cache, and BigPipe are all active.
Next, go to Configuration then Performance. You will see options for minimum cache lifetime, browser caching headers, and aggregating CSS and JavaScript. Enable CSS and JS aggregation for production.
For serious sites, go beyond core caching. Install Redis or Memcached for object caching to replace the slower database cache backend. Configure a reverse proxy or CDN in front of Drupal. Review cache tags and contexts in custom code to make sure everything is cacheable where possible. Good caching is the foundation of a fast Drupal site, so spending time on it pays off for every visitor afterwards.