How do I quickly join a group and use the intercom function?

How do I quickly join a group and use the intercom function?

Enter the same 6-digit channel number as your friends to join the group room on the Group interface.

Questions about joining a group
I am not receiving message from group members. How do I fix it? Why can’t I send a voice message? I cannot join a group. How do I solve this? Why do I lose sound when I connect to the intercom? Why can't I talk through the helmet when it’s connected to the app? iOS group cannot send voice?