how to get my earphones to work

When you plug them into the MicroUSB connector on the top of the phone, you should hear a beep and message.

If there's no beep/message, either the headphones are defective, or they are incompatible with the GR500/Xenon.

There are multiple standards for the MicroUSB audio connection.  Just because they have the right connector, doesn't mean the connector is wired in a compatible manner...
For example, most/all Motorola headphones won't work with the GR500/Xenon.