I have not taken part however, I wrote my thesis on ESG investment of institutional investors. If you are interested in becoming a professional on the topic I strongly suggest this Massive Online Open Course (MOOC) 'principles of sustainable finance' bij the Erasmus university (Netherlands), here you can find the link to the (free) course https://www.coursera.org/learn/sustainable-finance
Area's to focus on are risk assessment regarding climate change, divestment (coal, oil and gas for example) and new markets (renewables), overall most important is how investments contribute to reaching the United Nations Sustainable Development Goals (SDGs). The SDGs are often used to create 'Impact funds', however, take a closer look because it is difficult to measure the actual 'impact' of an investment.
Following ESG ratings and ESG indices (provide by for example Sustainalytics, MSCI, FTSE Russell etc.) are a start, however these funds do not necessarily differ much from regular investments, they keep out the 'worst' companies but well... I would say it is the bare bare minimum. If you truly want to have a positive impact with your money you need to be an active investor, maybe start engagement activities with the companies you are invested in..
I could go on forever, If you want to know more let me know!