What can I do about moderate scoliosis?

Depends. It will depend on your age and if you have had an evaluation. Scoliosis is a difficult problem and can get more difficult. See a spine surgeon or other specialist with an interest and expertise in scoliosis and get an opinion. Depending on age and condition, you may need bracing or may be a surgical candidate. Hard to know. Get an expert opinion.
Depends on age. Children before a growth spurt are generally braced for moderate scoliosis (cobb angles between 20 and 40). After skeletal maturity, these curves are merely observed. If a curve is non-progressive in adulthood, and doesn't bother the person from a cosmetic perspective, no treatment is necessary.