Avoid high temperatures and prolonged exposure to light.
Make sure that when storing your bag that it is not resting on anything else which could flatten or mark the pile. Ensure the the pile is gently smoothed into its natural direction.
As with other ‘finished’ fabrics, velvet is not intended for everyday use. Continual use will wear down the pile of the fabric and may cause patches.
To clean, contact a specialist professional dry cleaner.