When logging into any 2FA-protected service, you will get asked for a 2FA token. Normally you’ll have to open you 2FA app, find a proper token/code and rewrite it. With Broser Extension you can simply click a button next to the address bar or use a keyboard shortcut and the browser extension will send a request to the 2FAS app on your phone. Then you can decide whether to accept or refuse the request. If you accept, the app will automatically transfer the token to the plugin in a safe and encrypted way. The plugin decrypts the token and places it in the correct input.
Remember that the 2FAS app needs to be paired with the browser on which you’ve installed 2FAS Browser Extension.