However difficult, though, if you can learn to master a walk cycle then you can animate just about anything. There are many types of walk cycles, and you can vary the motion to match your character or his/her mood; you can do bouncy walks, shuffling walks, casual slouches. But the first and simplest is the standard upright walk, viewed from the side--and that's what we're going to attack in simplified form today.
You can cover the cycle of a full stride in 8 frames, as demonstrated by the above walk cycle--the Preston Blair walk cycle, one of the most common reference images in cartoon animation. Many Preston Blair examples are great learning references, and I'd advise you to save that image and use it as a reference throughout the entire lesson if you get lost--because we're going to go fairly quickly, to crunch this down to 10 steps with room to show the finished results. My first 2D animation instructor gave us a reference and a little advice and left us to discover our own individual rhythm and stride, and to learn by trial and error.
I won't be quite so cruel, but I do think that you'll learn this best if I don't do every tiny step for you and let you work some things out for yourself. So grab a flotation device, and get ready to dive in.