Your computers, phones, and other devices normally use the Domain Name System (DNS) server with which the router is configured. Unfortunately, this is often the one provided by your Internet Service Provider (ISP). These lack privacy features and also might be slower than some alternatives.
To read further on DNS and why it's not private go here , which is where the article is based on. Now, let's go to the point.
To change your DNS to Cloudflare which is faster and private, go to your router's settings and change the DNS, this change will apply to every device on your home network:
The article regarding Cloudflare DNS is here.
If you want to only apply it on device or browser lvl go here.