Hello student to prepare legal aptitude for LLB you may join coaching institute in your area in case it you want to prepare it by self study then please purchase a Book for legal studies in which all legal Chapters all type of law and Indian Constitution are available once you complete all the chapters start practicing question on legal aptitude the questions is on principle and facts.

Must solve atleast 5 previous year question paper.

Feel free to comment if you have any doubt

Good luck