CSS Icons:-
The simplest way to add an icon in your HTML page, so we are using is a icon library, such as Font Awesome.
Add the name of the icon class and library to any inline HTML element like <i>
Font Awesome Icons:-
using the Font Awesome icons , go to fontawesome.com, sign in and use.
<script src="https://kit.fontawesome.com/yourcode.js"></script>
Bootstrap Icons:-
Add a link in head part,
<link href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css">
Google Icons with code family:-
Add a link in head part,
<link href="https://fonts.googleapis.com/icon?family=Material+Icons">