WordPress has several solid ways to add Head and Footer code to any website. One way is via Theme Options. Most solid themes have an option to add Head and Footer code by just pasting it in. But many themes don't have this option.
Two of ways to get around this are with plug-ins. One is called Head and Footer Scripts Inserter by Space X Chimp.
Another is called Insert Headers and Footers by WPBeginner.
Recently when a client of mine saw a blank screen while trying to add Google Adsense code into Head and Footer Scripts Inserter, we solved the problem by pivoting over to Insert Headers and Footers.
Paul Hickey, Founder / CEO / Lead Strategist at Data Driven Design, LLC and founder of The Voice Event, and The Voice Designer, has created and grown businesses via digital strategy and internet marketing for more than 15 years. His sweet spot is using analytics to design and build websites and grow the audience and revenue of businesses via SEO/Blogging, Google Adwords, Bing Ads, Facebook and Instagram Ads, Social Media Content Marketing, Email Marketing and most recently, Voice App Design and Development – Alexa Skills and Google Actions. The part that he’s most passionate about is quantifying next marketing actions based on real data.