I put this in my themes header.php file above the PHP tag and it works. Keep in mind you must have an SSL installed on your site, and use https:// when visiting your site for the embed to work. Twitch will not allow an embed to work on http://
wp-content/themes/decode/header.php
<iframe src='https://player.twitch.tv/?channel=raquelly_&enableExtensions=true&muted=false&parent=disc4life.com&parent=www.disc4life.com&player=popout&volume=.001' frameborder="0" allowfullscreen="true" scrolling="no" height="300" width="525"></iframe>
Also you can check out this post here Automated Embedded twitch video iframe using Twitch API and bash