Most type foundries won’t license their typefaces to be used on the web because there is no openly supported closed font file type. Each service seems to have a different take on how to deliver type on the web and how to charge for it.
Free versions come with challenges—they may have limited options, or they have horrible hinting and kerning tables, or none at all.
For demonstration, I chose Roboto Regular, you may change the font after you successfully apply this external font.
<link rel="preconnect" href="https://fonts.googleapis.com">
<link rel="preconnect" href="https://fonts.gstatic.com" crossorigin>
<link href="https://fonts.googleapis.com/css2?family=Roboto+Slab&display=swap" rel="stylesheet">
If you want to learn more about Google Fonts and implementing it, check out this resource: https://developers.google.com/fonts/docs/css2