If you have access to an Eikon application, you can open a quote window then enter the CUSIP in the search box. As you type, suggestions (including the corresponding RIC) will appear.
If you don't have an Eikon application you can use the RIC search tool available under the Dev.Tools section here .
Thank you for the reply. I am currently developing application using the Elektron Transport API. I would like to know what if I only have CUSIP information, how can I request market data with CUSIP in ETA?
At present if you only have CUSIP information and wish to consume data from a realtime feed using ETA then you will need to first convert the CUSIP to a RIC. See this thread which talks about using our DataScope Select service to lookup a RIC from a CUSIP.