GA FB Pixel 3rd party
The easiest way to do this is in your Admin Dashboard - Extensions - Extensions - Dropdown Analytics - Google Analytics (edit icon).
You may need to click the install (+) button first and then once installed click on the Edit button which will appear there instead of install (+).
Any third-party embed code that needs to go into the header, you should place there one under another.
Please remember that after you have done any changes in your website Admin Dashboard you will also need to make sure that you cleared all the cache from your store. For this do the following: Go to System>Tools>NitroPack> Click on Clear Cache on the top right and from the drop-down menu click on "Clear All Cache" and you will be able to see changes loaded on your front page. Take a look at the picture example: