Keep it, or let it disappear.
Messages stay in the history by default. Set a timer before you send, and that message clears itself for everyone.
Disappear timers, set per message
Use the email and password your admin set up for you.
This is how the group sees you.
Your name color marks every message you send, so people can spot you at a glance.
Pick a name and color. You can change these later.