If you want to appear for the civil services IAS exam, the first thing you need to do is to complete your mechanical engineering degree and graduate. You cannot become an IAS till you graduate. The second thing you need to do is to understand the content of the exam. You would need to have top of the line knowledge of history, geography, and current affairs among others. You should either have an inherent interest in these subjects or be ready to toil hard to master them. Therefore, your goal requires you to study very very hard over the next few years. Break up your goal in two steps. First, study hard to complete your mechanical engineering degree. This is the easy step. Second, build and execute a study plan to take up the civil services exam. The second step will require you to study much harder than the first.