The National Institute of Allergy and Infectious Disease (NIAID) now has a sample NRSA fellowship application and accompanying summary statement available on their website.
If you're writing an individual F30, F31, or F32 pre- or postdoctoral NRSA application, it's helpful to see examples of successful applications. Ideally, you would read a specific example of the type of grant you're applying for, whether its an F30 MD/PhD fellowship, an F31 predoctoral fellowship, or an F32 postdoctoral fellowship.
However, the basic structure of an NRSA fellowship application is very similar across mechanisms. NIAID recently posted an example F31 Diversity Fellowship application on their website, along with the accompanying summary statement. Through this example, you can see how this student addressed all the required sections - such as Responsible Conduct of Research and the Research Training Plan - and how the reviewers responded to it.