There are various types of job profiles open with RBI each year. Positions such as clerk, assistant , manager and junior executive are being filled on regular basis. The process for exam is online as well as offline in some places.
In order to apply to the exam, you have to check the exam the schedule. Also check the eligibility. If you are eligible for bank PO then you'd be eligible for any exam from the RBI.
After competition of exam, you'd be undergoing the training and other recruitment process depending on the position.
Here is the URL : https://opportunities.rbi.org.in/Scripts/Vacancies.aspx
You can read more about vacancies and process for the RBI here. You'll also find the option to register for online exam on this URL.