If your on windows what I did was download jpexs free dash compiler (https://github.com/jindrapetrik/jpexs-decompiler/releases) and click on the one made for whatever computer you have (this didn't work on its own for me but you can try for yourself because some computers are different than others.) then after that I had to download Java (https://www.java.com/en/) find the version that works for you (Windows, Linux, ect.)
after doing all that you can watch a video on how to do the rest. hope this helps :)