The easiest way to link CSS to HTML is by using an external stylesheet. Create a CSS file, such as style.css, and place your design rules inside it. Next, open your HTML document and add <link rel="stylesheet" href="style.css"> within the <head> section. The browser will then load the CSS file and apply its styles to the HTML elements. This approach keeps your HTML and CSS organized separately, making the website easier to update and maintain. External CSS is particularly helpful for business websites because the same stylesheet can control the design of multiple web pages consistently.