Included below are some links directly to volunteering applications pages of two different park service programs. They are the perfect way to get started if you are new to volunteering, or even just want to get back into it.
https://www.nps.gov/ever/getinvolved/volunteer.htm
This is the website for the National Park service, which offers different programs for both volunteering in events, and longer term positions
https://floridanationalparks.org/volunteer-with-us/
Thisa website for specifically Florida national parks, where they additionally have similar options for volunteering, but they are more tailored to the everglades themselves rather than all national parks in the state.