You are 21 years old, you are sure that you want to join a cricket academy and have a future in cricket.
There is no age limit for learning cricket. Umesh Yadav, was 20 when he was asked to try leather ball cricket. Pravin Thambe played in Ranji trophy and IPL at the age of 41. So, if you have the passion, determination and the right guidance, you can do it. Cricket academies will have summer camps and training programs for various age groups.
Start playing at the local club level, get in touch with your college or town teams and start playing matches. Meet players and coaches who are being groomed for Ranji trophy or who have already played at this level. Make the best of these chances to impress and learn from them.
Hone your skills of batting, bowling and fielding, all rounders have a better chance in the short version of the game. Make videos that showcases your best batting techniques, inswingers or yokers, excellent stumping or athletic fielding. Refine these and keep posting them on social media.
Look out for talent scouts and cricket talent open days, wherein you can perform and impress people who can lead you to the state and national teams.
Now that the IPL is starting, approach your IPL team and become a fan(https://www.royalchallengers.com/rcb-world/rcb-fan-first-initiatives) or at least enroll as a volunteer for the teams or the stadiums close to you. You can get a chance to rub shoulders with players, coaches, physios etc who can give you the crucial break.
You can contact the cricket academy directly and enquire (http://www.kioc.net/node/176). For instance Brijesh Patel Cricket Academy has eligiblity of candidates above the age of 6. You can approach such academies and enroll yourself.
Focus on your fitness and diet regimen. You may need to think of enrolling into an elite cricket coaching school that has very good contacts with national and international players as you need to get trained and breaking quickly.
Search for golden chances like this (http://www.vdcrickethunt.com/). a cricket talent hunt open for the ages 13-30 years.Even if you do not succeed, you will get contacts, people who can help you achieve your goals.