Hello

Thank you for your query.

You can use the following methods:

1. Template (Helix) Options > Custom Code > Header -- put your code there*

OR

2. Install Google Analytics Plugin from JED (Joomla Extension Directory), put your ID and publish.

And, also could you kindly check out the blog link below?

https://www.joomshaper.com/blog/how-to-install-google-analytics

You will find the steps mentioned here for Helix ultimate based templates.