If you've filed a completed VA Form 9, you are not required to submit any additional paperwork. The Board of Veterans' Appeals (BVA) will evaluate your appeal based on the same evidence used by your Regional Office (RO) when it made its determination on your original claim, along with your VA Form 9 and the Statement of Case (SOC and the Supplemental SOC, if there is one).
If, however, you have additional evidence such as records from recent medical treatments or evaluations that you feel substantiate your disability and make your case stronger, you can submit the evidence to the office holding your claims folder. (See FAQ: "Where is my claims folder kept?") An experienced attorney or advocate can also submit additional written information in support of your claim.
If, after considering the new evidence, the RO still does not approve your claim, you will be provided a Supplemental Statement of Case. The new evidence you submitted will be included in your claims folder and considered when the Board reviews your appeal.