To start a group chat with other team members click on the "plus" icon and input the user's name or email address. Click on the search result. Repeat this action to each user you'd like to add to this chat. When done Go to chat.
When a group chat is created you can change its name, it may be helpful to identify chats on the list if you're added to the numerous number of group chats.
To mention a specific user in a group chat use the @ symbol, like this @username
To check the list of users added to the group chat click on the users icon in the upper right corner.
It is not possible to leave or add new members to the already started group chat.
Group chats contain all the same options as private chats. You can learn more about private chats here.