This site, made by the friends of Google Fonts, cover everything about Variable Fonts and show you how to get started. Google Fonts have even included variable fonts as one of the filter options on it’s own site.
BEWARE though, make sure you also read the performance article about Variable Fonts below and understand when to use them and when to stick with static fonts.
Welcome to the most radical change in type since Gutenberg. Variable fonts let you add nuance and artistry to your web typography without bogging down your site. Now you can accomplish what used to require several files with a single file and some CSS!An excerpt from A Variable Fonts Primer