First you need to know the entire syllabus for the exam. Topics included in this exam are

Business Communication

Legal Aptitude and Logical Reasoning

Economic and Business Environment

Current Affairs

Presentation and Communication (Viva Voce)

You'll get the study materials from the official website of ICSI i.e https://www.icsi.edu/student/study-material-os/

The study materials are in the form of mock tests, video lectures and printed information are available in the official website of ICSI. For Current Affairs, you should read newspapers thoroughly.