Go to Controls Panels > Look & Feel > Customization (tab) and enter you Google Analytics account number in input labeled "Google Analytics account number". Save the form and that's it!
GTag
If you wish to use latest gtag.js for more advance analytics data reports, rather than ga.js, enable "Google Global Site Tag Mode" option right under "Google Analytics account number" form field.
Note: if the Customization tab isn't visible
You might need to enable advanced preference filters.
This is found under Control Panels > top leftmost icon (this button appears similar to the "Tesla" logo) > Preference Filters > Advanced.
Short cut
There are other ways to accomplish the same. This method below may not be best practice to connect your tiki site, yet it works.
Dot html index file
Create a dot html index file and place your GA code at root.
So that there is no supersedence issue, when you create your index file add a language extension.
Example of a shortcut
Your .html file can be named like this:
index_en.html
Check with your system administrator if your not 100% sure.