The first thing you will need and the most important thing is to be Determined. You can't just do a 3 kilo meter run on Monday then half a kilo meter on Tuesday, what you should do is a 4 kilo meter run and keep adding as you go on .
Practice makes perfect but in this case perfect isn't good enough world class athlete is where we wanna go so you need to really work and push yourself to your limit, especially practice on things you want to work on like if your focus is shot put I encourage you to do 10 push ups each night this will get very easy over time and you will shorty be able to do 20 then 30 40 50 and so on
Control your diet . To be a world class athlete you need to eat like one The best thing to eat is raw eggs broccoli rice, and a gallon of water every day . Never eat any dairy products don't even think about fatty food unless you want to become the least athletic person in the history of human beings in that case feel free
If you follow these steps correctly you will be a top world class level athlete and if that dose not work go google it