Great that you are looking for a way to contribute to something meaningful. OpenStreetMap aims to create a free map of the world, at detail levels nobody else does. Besides the obvious, it helps groups that are marginalized (how do I navigate as a blind person? Where are safe spots to cross the street? Does this restaurant not only have a ramp for my wheelchair, but does it also have restrooms that accommodate for my needs?)
The simplest way to start is to contribute on pic4review.pavie.info - here you can basically look at pictures other people have taken, answer some questions and thus add data to OpenStreetMap.