The vox will not work until you set the Mode Switch to Vox. Always be careful not to leave the vox mode on because the rig will key up when your dog barks.
To adjust the vox, pick a empty frequency for testing. Watch the PUSH-TO-TALK button light up to blue when you speak and return to black when you are quiet.
The DWELL setting controls how long you must remain silent before the rig returns to receiving. I like a setting about one second, maybe longer.
The LEVEL setting works reverse to what many people expect. This setting is the S-Meter level that will key on the transmitter when you speak. If you set it to the left, the Vox becomes more sensative. If you set it too low, the rig will transmit your breathing and typing sounds. If you set it too high, it might miss part of the first word. I like to set mine about 7.