You would need to use a WordPress function "do_shortcode". Codex link
<?php echo do_shortcode( '[instagram-feed]' ); ?>
Possible Response:
You can use the function "do_shortcode()" to display the feed directly in the template. For example:
<div>
<?php echo do_shortcode( '[instagram-feed]' ); ?>
</div>
The php tags before and after the code are not necessary if you use this inside an existing block of php code.
Let me know if you need any more help with this!