Migrating from Glyphicons to Font Awesome is quite easy.

Include a reference to Font Awesome (either locally, or use the CDN).

<link href="https://maxcdn.bootstrapcdn.com/font-awesome/4.7.0/css/font-awesome.min.css" rel="stylesheet">

Then run a search and replace where you search for glyphicon glyphicon- and replace it with fa fa-. Most of the CSS class names are the same. Some have changed though, so you have to manually fix those.