Read the Risk & Stakeholder Management chapters of the PMBOK Guide as well as PMI's Risk Management Standard. You might also want to peruse the archives of Dr. David Hillson's monthly blogs (going back at least a decade!) on the subject...
In addition check few articles related to PMI-RMP on pmdesire.com.
Review PMBoK 5th/6th Ed. Risk Management chapter thoroughly;
Study PMI Standard for Project Risk Management;
Review Rita Mulcahy PMP prep book Risk Management chapter;
Study Abdulla Alkuwaiti RMP prep book;
Review PMBoK 5th/6th Ed. Communication Management chapter;
Review PMBoK 5th/6th Ed. Human Resources Management chapter;
Review Monte Carlo simulation technique;
Study Latin Hypercube technique;
Perform Practice Tests using Rita Mulcahy and Abdulla Alkuwaiti prep books. Saving Changes...