Automatic free gift to cart without code/ adding specific article to cart

[woolrex]

I want to gift my customers with a free product if they buy a product within one collection (Baby-Schlafsack). This should automatically appear in their cart. I don't want them to put the gift item in the cart or to enter a voucher code.

And I don't want to install an app as we have - beside the above case - no further need.

Our shopify theme is Dawn. I cannot install script. But I am sure, there must be a possibility to enable a code

I found https://jayanetty.com/blog/give-free-product-using-shopify-script-editor/ but cannot use it as we have neither the opportunity using adding skript editor nor Dawn contains "cart.liquid" 

[jazz-jay]

Hi,

If you do not want to use any app to do this OR you can not use the script editor. Then you need to edit your theme codes to do this. It's not that simple though.

[woolrex]

I know but its worth to me

[jazz-jay]

✓ Just do it !

[woolrex]

I would do but I need help with the code. That's why I created this post