Just want to note that physicalism =/= atheism. There are theistic physicalists (eg Thomas Hobbes) and non-physicalist atheists (eg David Chalmers). Atheism is the belief that there is no God. Physicalism is the belief that reality is made up of entirely physical stuff. The two viewpoints are not necessarily related.

Check out dhammatalks.org. It’s a great resource. The landing page has a “for beginners” section which may be helpful for you.