Which are books we prepare for CAT,GMAT,SMAT....??

For preparation you can refer to following reference books as per your choice and understanding :
1) How to prepare for Quantitative Aptitude for the CAT How to prepare for Data Interpretation for the CAT How to prepare for Logical Reasoning for the CAT How to prepare for Verbal Ability and Reading Comprehension for the CAT
All by Arun Sharma and Minakshi Upadhyay
2) Pearson Guide to Quantitative Aptitude for CAT by Nishit Sinha Pearson Guide to Quantitative Aptitude and Data Intrepretation for CAT by Nishit Sinha Pearson Guide to Verbal Ability and Logical Reasoning for CAT by Nishit Sinha There are others books like Word Power Made Easy by Norman Lewis, High School English Grammar and Composition by Wren and Martin etc to help you for your preparation.
There are websites offering free and paid CAT coaching and also there are YouTube channels who can help you regarding the same.
You can also join various coaching institutes like TIME, CL, IMS etc or the online coaching institutes also for concepts and mock tests.
All the best!