Created in 2006 by educator Salman Khan, Khan Academy is one of the original free online-learning institutions. With step-by-step video tutorials, you can  learn how to program drawings, animations and games using JavaScript and ProcessingJS, or learn how to create webpages with HTML and CSS. See, especially, Khan's "Hour of Code," designed to introduce students to one hour of computer science and computer programming.
I recommend checking out CS Dojo, TheNetNinja, and Harvard’s CS50 YouTube channel. If you don’t have time to search for a perfect coding video or channel, you can also check out LinkedIn Learning’s vast video library for vetted and professional-looking tutorials. While the service’s $30/month subscription fee is nothing to sneeze at, you can binge-watch an unlimited amount of content and topics—making LinkedIn Learning a better deal than other on-demand online classes that come with annoying restrictions.
By recreating existing projects, you’ll learn more about the inner workings of your highly customizable device. You might even find yourself inspired to create new ways to use your mini-computer and delve further into the world of code. (You can even enroll in UC Irvine’s The Raspberry Pi Platform and Python Programming for the Raspberry Pi Platform class through Coursera, if you want a little help getting started.)
Take a few minutes (or a day) to think about the reasons—the real reasons—why you want to learn a programming language. Be honest with yourself. Are you trying to learn the barest minimum to score a promotion? Are you looking to make a big career change? Do you want to create the next greatest app? Thrill your roommates by programming your various smart devices to do something awesome?