By default Voice Chat is enabled, so be sure that on your PC your Input device is set to your HMD microphone. There are options in the Player Menu to enable push to talk (B button on Rift), disable your own voice chat, or to mute other players. The Voice Chat is proximity based, so you will hear people nearby and not hear people far away. Just talk in a normal inside voice, there's no need to shout.
Speaking at a Distance
The compass can be used for your "Party" and "Fellowship" voice chat. Grab the compass and hold it near your mouth, you will see the compass turn Red, this means you are broadcasting. To switch channels between the Party and Fellowship chat, simply press the trigger while holding the compass and it will toggle between the channels. Your compass is set to Party chat by default (Purple Stone core).
You may also send written (Typed) messages in game to players on your Friends list. To access messages that have been sent to you open your Player Menu, and select the Messaging icon (Closed Letter). Here you will find your Inbox will all the messages you have received. To send a new message to one of your friends, open the Player Menu and select the "Social" tab (Multiple head icon). Find the player you wish to send a message to and select their name, you will see a menu appear with the option to message them. Simply type in the message you wish to send and click send. There are a few pre-written messages you may use to speed up the messaging process.
You may also send written messages to players in response to LFG posts. To write your own post or to see available posts, open your Player Menu to the Activities tab and select Looking For Group. Respond to a listing by clicking on it; by default, the message will be pre-loaded with your current class and level.
If you are feeling overwhelmed by your surroundings, or have found someone harassing you or other player, you can use the Personal Bubble feature. By pressing both Menu buttons at the same time you activate a 5 minute mute to everyone in game, there will be a small animation at your feet and a noise to signify it has worked. This will not only mute all players in game, but will also hide their hands. To discontinue use of the Personal Bubble, simply press both Menu buttons again.
Alternative Communication Methods
The OrbusVR community has an unoffical discord channel with a number of open text and voice channels for anyone to use. Many fellowships opt to use this or their own dedicated discord channels for their reliability and the fact that voice does not taper off with distance or in-game orientation. It is highly recommended to disable in game voice chat temporarily when in the same area as those in the chat as the echos can be very distracting. Some players keep Push to Talk active, allowing them to switch between talking to their discord and talking in the game.