Kickboxing can be used as a means of self defense or as an alternative way to get in shape. Ideally, you should train with a qualified instructor before you attempt to learn how to kickbox on your own, but in the modern age, there are a host of online resources at your disposal to learn the fundamentals of this striking art.
Peruse the internet for an online kickboxing course that suits your needs. Decide whether you're looking for an aerobic workout or an actual combat-oriented class, which will narrow your search considerably.
Follow the instructions of your virtual kickboxing instructor and watch the videos provided as many times as you need in order to retain the lessons. To learn anything, repetition is key, so you need to practice often and in the order the instructor suggests.
Supplement your online lessons by doing independent research on your own. Find kickboxing blogs, tutorials and compare the lessons you're being taught to other instructional sources. Watch professional kickboxers train and fight on YouTube to get a sense of how the pros move.
Reach out to other students and your instructor if you have any questions on technique and form. Most online training sources will have forums where lessons are discussed by other students taking the course. These can be valuable additions to your training.
Try out kickboxing classes to mix things up and get some hands-on instruction. Online courses may work for some, but there's no substitute for the real thing. The more experienced you get with the fundamentals of kickboxing, the more effective you'll be at absorbing and retaining online instruction.