Hi

So you say you want to become civil engineer. Here is the procedure

First of all you need to finish your 11 std in science you have to take maths as one of the subject because maths is compulsory for engineering admission, and when you are in the 12 std you can start applying for various exams.

Civil enginnering is offered by many colleges in India, but not all the colleges are good for eg

Your top priority should be IIT or NIT

Now if you want to get into this college you will have answer JEE Main and JEE Advanced. NITs accept JEE Main and IITs accept JEE Advanced. 

If you want to crack JEE you will have to start preparing for it right from 11 std. Take some tution.

Now if you cannot get into IIT or  NIT, you should try for some top priviate universities in India. Like Manipal University or VIT

Now some private universities accept JEE Main marks, but majority of priviate colleges conduct there own entrance test.