Get a cleaning. If it's been awhile since you last cleaning then I recommend you go in for one. Bleeding can indicate gingivitis, periodontal disease, or in rare cases something worse. It's best to see a professional for an evaluation.
Soft brush. Use a soft brush, brush lightly including the gums even if they bleed, and use floss. Over time, they will stop bleeding. Make sure to follow up with your dentist.