CSS
@import url(https://fonts.googleapis.com/css?family=Roboto);
HTML
<link rel="stylesheet" href="https://fonts.googleapis.com/css?family=Roboto"/>
body{
font-family: "Roboto";
}
<!-- To Add Montserrat font or any font as such -->
<!-- Go to https://fonts.google.com browse the font you like here, Montserrat-->
<!-- On the right click embbed and get the link similar to one given below-->
<link href="https://fonts.googleapis.com/css2?family=Montserrat&display=swap" rel="stylesheet">
<!-- add this ^ link inside your <head> tag i.e. before </head> -->
<!-- In css you can specify the font family as -->
font-family: "Montserrat", sans-serif;
<!-- To import google font add this to the head of your HTML then you can use use the imported font family in your CSS file -->
<link rel="preconnect" href="https://fonts.gstatic.com">
<link href="https://fonts.googleapis.com/css2?family=Open+Sans&display=swap" rel="stylesheet">