This link should help, Vicki:
Hi ! First you need to make sure you don't have a leak and or water damage . Once that is taken care of make sure your insulation isn't covering the soffit area , that needs to be clear to allow ventilation . You could put in an attic can , ours turn on automatically once the attic reaches 90° F . This help to keep it cooler in the attic and helps to keep down a/c costs .
Yes, check for any water leaks first! Put in soffit vents and/or an attic vent to allow more air movement. Be certain the issue is mildew and not mold!
Put bleach in a spray bottle and spray it wear a mask and ventilate if possible protect ur eyes as well
charcoal. I had an antique dresser and the drawers had an awful musty odor from sitting in the garage for years. I put some charcoal wrapped in newspaper in each drawer and it did the trick. An antique shop owner clued me in on this. Worth a try. Make sure it doesn't have starter or lighter fluid in it. PLAIN charcoal.