This is a very generic question which you can find tons of links on Google.
Do you have any specific questions after you start building the dataguard?
thanks for your reply,
I didnt found any official document to configure dataguard from oracle rac to stby single node.
if you have any document step my step, i would be very thankful.
and again you have a tons of links on the internet.
Here is how I set it up: How to Create a RAC Standby Database
Now you won't be creating a RAC standby. But follow those instructions up to the section marked Convert Standby to RAC. This document first takes a RAC primary and makes a single-instance standby out of it. Then the last section converts the single-instance standby to RAC. You'll be skipping that step.
I also have this document: How to Create a Physical Standby Database
Which does not cover RAC, but shows how to create a standby. It may be helpful as well.