With a little knowledge and a few hours of practice, even fairly small children get quite good at it. Let's discuss what I consider the basics so you can get to practicing. Not all tomahawks are created equal, and there is no doubt some of them are very difficult to throw well because of the way they are made. You can throw one of that size for a long time without tiring, and it also will allow you to have better control. Length is important, too, very important.
Most tomahawks come with a handle which is too long.
Because of the physics involved, there is an easy way to find a proper length for you. Make a fist. Measure from your knuckles to the tip of your elbow. That length should be the overall length of your hawk, including the head. A simple tomahawk is best, and ones with complicated configurations may not throw well.