Here's How:
1. First, kill the mold by:
2. Brushing the mold and mildew from the material.
3. Wash the affected area with a solution made up of 1/2 cup Lysol to
a gallon of hot water.
4. And/or rinse with a solution of 1 cup of lemon juice and 1 cup of
salt to a gallon of hot water.
5. Allow the material to dry in the sun.
6. Next, bleach the mildew stain.
7. Wash or soak the affected area with one of the following,
depending on the material.
8. For most fabrics, you can use a non-chlorine bleach.
9. For coloured fabrics, use a solution of 1 cup of lemon juice and 1
cup of salt to a gallon of hot water.
10. For colour safe fabrics, use a solution of 2 tablespoons of
bleach to a quart of water.
11. Allow the bleached area to dry thoroughly.

Alternatively you could purchase a product like Mold Off
http://www.moldoff.org
Good Luck!