You do not need to add Yoast if you only want to add meta tags to the homepage. Just some minor editing will save you on performance.
You can use the is_home() function.
Insert this to your header.php
:
<?php if (is_home()) { ?>
<meta name="description" content="Your description for homepage..." />
<?php } else { ?>
<meta name="description" content="Description for other pages..." />
<?php } ?>