How do you train for the 100m, 200m, and the 400, sprints?

Hi, im 13 years old and i want to know how to train for the 100m, 200m, and the 400, sprints? My times last year were 100m-13.17seconds, 200m-31.38 and 400m-1m:3 seconds
Are these good for a 12 year old boy???
since now im 13 please help me find a way to improve them.
thnx