Hi,
You can try using the plugin ultimate google analytics which is highly recommended.
Another option is installing Yoast all in one seo plugin which also has a place to place your analytics code.
I agree also with chathrinetina that you can add it directly in the footer.php file.
I did so in my site https://paypal-bingo.co.uk and I recommend doing so in a site / blog that has already enough plugins installed.
Cheers