How to save the world
How to work unattached to outcome. To do the work for the work's sake, not expecting any fruits of your labour nor being attached to results or outcomes.
This is karma yoga. This, is seva (selfless service).
Any work can be performed in this way, it doesn't need to be as a designated volunteer with a specific organization or formal group whose mandate is to "help" people.
It is work offered up.
It could be cleaning the toilet, it could be performing one's job in a way that is light and dedicated and to the best of one's ability.
We don't have to leave our homes to save the world.
We can save ourselves, the world will follow.