You can click on the name tag above a user to open their profile and add them as a friend. Once they accept, you can send them messages from your Oculus home menu, and even from the Oculus app on your phone. In this menu you can also view their friends, creations, and send them a party request.
Once you have made friendships and start to collaborate on worlds you may want to utilize Oculus Chats or Facebook Messenger. Through there you can even create group chats.
COMMUNITY GROUP precedes this tutorial
Seen above is selecting a name tag by clicking the index trigger.
Seen above is sending a friend request.