Everything Philippa said! Though re the faux pas, do you mean in terms of naming the agent specifically or not saying that it’s being read at all? Because I’ve always been told it’s good to let other agents know that you’re sending it to other people, that other people are reading the full etc. and this is what I did when more than one person was reading mine and no one seemed to mind. (Or maybe no one told me!)
DMs – I’m not sure if there is a quicker way but if you click on members and find the person you want to send a message to, you then click on their profile and under their name there’s an option to send them a public or private message.
Good luck, Pinks!