Adding script to header is just login page

I need to add some script to the header and body tag of JUST the login page. I'm not clear on how I go about getting it to appear on just a specific page. One piece of code needs to go before </head> and the other before </body>.

I need to add some script to the header and body tag of JUST the login page.
Please elaborate in detail what script you are attempting to add

It's some script that will control a multivariant program being run by an outside company. We need to install on script on the product page and one on the login page. Thanks!

It's some script that will control a multivariant program being run by an outside company.
Login should be a secure page....Again what is being gathered/shared by this script and why/what do they need with login info?
Or explain "In Detail" what it is and not just that it is "multivariant ", which says nothing

The script for the login page will be called securely.

Before </head> I need to add:

Before </body> I need to add:

Before </head> I need to add:
Those instructions are not for ZenCart...
See this tutorial and the sectiopn on "Extra Javascript for an existing file"
https://www.zen-cart.com/tutorials/index.php?article=230