You can rename new or existing conversations on any device by going to the group conversation settings page.
To name or change a name in the desktop application
Click the information icon (the letter ‘i’ with a circle around it) in the top right corner.
Click the current group name
Enter the desired group name, then click done to save your changes.
To name or change a name in the mobile application:
Tap the group name at the top of the screen when you are in the conversation.
Tap on the blue “Edit Name” button
This will allow you to start typing in a new name or change the name of the group.