Add Javascript in Debut theme - where? (Optinly form app)

Store Design
1

I have an app called Optinly and I want to add it to my Shopify store. Tells me to do this:

“Paste the copied script code in your root index.html file within the body section.”

This is the code (part of it)

<script id="optinly_script" async="true" data-app_id='010e4f68-XXXXXXXXXXX</script> <p>Could someone help me understand where to paste this? Thank you very much.</p>
2

@appcrazee - please open your theme.liquid file, you will find tag in it and paste this code after it, if you find it very difficult then can you please add me as collaborator? I will do it