[neutrak]

:privmsg <user>: <message> will get what you want but if possible I recommend compiling the latest build from github, as there is already an alias that links /msg to privmsg in that code.

You can also use /hi in recent builds (not sure what version you're using) to start a PM conversation in a faux channel.

Edit: Note that you can also add aliases with the /alias command, if there's anything else that you find unintuitive. Accirc works a bit differently than other clients in that it draws a distinction between server commands (denoted with : and sent as raw text to the server) and client commands (denoted with / and handled internally by the client). Some new users find it helpful to alias. I have included some default aliases in recent builds, including /quit for /exit and /join for :join, among others.