Use the Fast Color Corrector to crush the "Blacks" (lowering the input black level). Since noise is most visible in shadows, making them darker can effectively hide the grain.
Noise—grainy specks of digital artifacts—is the enemy of clean video footage. Whether you shot in low light, used a high ISO, or are dealing with compression artifacts, Adobe Premiere Pro CS6 offers several methods to clean up your image. denoiser premiere pro cs6
When denoising in Premiere Pro CS6: