hi,

see to prepare a competitive exam you must be really dedicated and must have a decent routine to maintain your work. however besides your bachelors course and college curriculum you may only invested 3-4 hours a day to prepare for exams like CAT, mat cmat etc. however  the syllabus for each of the exams is quite similar to the syllabus but I would suggest you to focus on CAT, since cat score is accepted in most of the Indian Institute. first of all go through the sample syllabus and some of the previous years papers. questions makes from english, logical and quantitative aptitude, reasoning. so you have to prepare the all the sections since sectional cutoff is required for college admission.  so from now on dont make tension and try to relax and focus on your studies. another  main thing is you have to practice mock questions. now a days various online platform available where you may purchase and give free test.

hope it would help.