Learn about NSF rotator positions here: NSF Temporary/Rotator Programs.
If interested in applying for a rotator position, job opportunities are listed on the https://www.usajobs.gov/ website (search for "NSF". Rotator positions will say "full time-temporary" in the position info section of the job description). For an overview of the application process, visit: https://www.nsf.gov/careers/apply/erecruit-overview.jsp.