It's mainly focused on how to do good with your career but 80,000 hours (https://80000hours.org/) has a lot of resources and articles about basically what problems out there make sense to tackle and then career pathways to do so. Alternatively Effective Altruism (https://www.effectivealtruism.org/) has a bunch of resources more closely aligned with just understanding how to do the most good possible. If you're looking for something more one-off and easier rather than a career change or something significant, I recommend Givewell.org which ranks some of the charities that they've verified do the most good at the lowest cost and donating to one of them!