Not sure that its available on android or iOS devices. Digging a bit it seems there's versions for major platforms like windows, mac, and linux, and even a plugin for touchscreens, but that only seems to support windows variants like Surface, Surface Book, Surface Go. Apparently in the pipeline for future versions, but thats down the pipeline. There does seem to be a bit of a community hack floating around, but you can also find some alternatives to Aseprite for android here.