Teams in Lumi are a good way to send messages to a whole group, and to be able to view what roles other people in your project have.

To create a new Team, go to Teams in the left hand column and press the plus

Give your Team a name, and upload a photo if you would like. 

Press this icon on the top right of each Team to add Users

Simply type to search their name.

To FYI your team, press the paper aeroplane in the top right corner then search for the team name, type a message and send.