By call it <head> Drwyd means, click the yellow tag icon on the Infobar, and Name the placeholder rectangle <head> and press Add. That is what you meant? This forces the text to be placed in the <HEAD> portion of the HTML document.

Then copy and paste your Google code in the Website Properties > Placeholder > Replace with HTML Code text entry window.

In WD6 there is also a text entry window on the Website Properties > Website page, Tracker Code which used to insert the Google code in the correct place. But I am not sure if that still works or not. The placeholder method is probably the best route.