I didn't gave any entrance exam for MBA. Now what are the things I can do in my career basis, currently I am pursuing my b. Tech(mech).

Hi, Incase you are pursuing B.Tech and interested for MBA (which many students are) so you can start preparing for MBA entrances from now on because getting admission in MBA colleges is not a big thing but from a reputed institute is what matters.
So prepare for CAT, MAT, XAT, CMAT etc and then give this year the exams. Forms will start after Sept/Oct this year.
Meanwhile you can also take some coaching if  you require.
All the best.