Hi,
     If you want to become a mechanical engineer you have two paths.
First one : Do 10+2 and crack JEE main and Advanced exam with good rank for admission in IIT's , NIT's , IIIT's etc. or BITSAT .These are the most reputed colleges with best placements in Mechanical Engineering.

Second one : Appear for Polytechnic course and find any best government poly technic college for pursuing diploma. Do diploma in mechanical engineering and learn the concepts. You can get placements after doing diploma too. Then you can even pursue degree in mechanical engineering.

Both of these paths need hard work and dedication. You should be dedicated enough. Do not try to cram things learn by concepts.

All the best.