There are various positions one can get hired in L&T. There are 2 ways to enter just companies.

First, study engineering in top rated engineering colleges and perform extremely well.

Second, Understand your interest, civil engineering in your case, do internships, gain experience and skills in your domain and later apply in this company.

You can check L&T recruitment requirements and what all profiles they generally hire.

L&T Careers

Just make sure it is not just the academics but your skills and excellence in your field which makes you unique from other candidates.

Good Luck.