The NIH public access policy requires scientists to submit final peer-reviewed journal manuscripts that arise from NIH funds to PubMed Central immediately upon acceptance for publication. If you do not comply with the policy, it may delay or affect your ability to get funding in the future. They have a series of video tutorials available at their site. Link.
In addition, the OSCTR provides a very brief PDF tutorial that may help you quickly comply with this policy. Download.
If you need assistance, as always please feel free to contact the OSCTR.