If you want to know how Bitcoins work, start with the Satoshi Whitepaper and proceed from there. I am sure it will automatically lead you to other resources when you try to understand some parts of it.
If you just want to use them, just use them, there is not really much knowledge needed for that.
If you are interested in the anonymity of it, look around the Darknet market communities.
If you just want to be involved in a general Bitcoin community, try Bitcointalk