The command M-x erc will start ERC and prompt for the server to connect to. If you’re unsure of which server or network to connect to, we suggest starting with “irc.libera.chat”. There you will find the ‘#emacs’ channels where you can chat with other Emacs users, and if you’re having trouble with ERC, you can join the ‘#erc’ channel and ask for help there.
If you want to place ERC settings in their own file, you can place them in ~/.emacs.d/.ercrc.el, creating it if necessary.
If you would rather use the Customize interface to change how ERC works, do M-x customize-group RET erc RET. In particular, ERC comes with lots of modules that may be enabled or disabled; to select which ones you want, do M-x customize-variable RET erc-modules RET.