I am 42 years old and was told that I have age related macular degeneration what can I do to preserve vision?

Correct diagnosis? At age 42, you are unlikely to have age-related macular degeneration. That is a disease of people aged 50+. I would see a retina specialist to confirm the diagnosis.
Macular Degen @ 42. As a retinal specialist, I have seen atypical macular degeneration present in the 40's. It is uncommon. Family history can be relevant here. Preserving vision depends on the severity of the amd (age related mac degen). The ared's study indicates that certain nutrients are beneficial to stage 3 and 4 amd. Have regular eye exams with dilation and when indicated Fluorescein angiography and oct.