HDMI mini box installed unable to watch DVD's

Recently had to have someone come out and install the required HD mini box. I am now unable to watch DVD's or VHS tapes. Any suggestions on how everything should be connected at this point? I did not use the coax cables for older model TV's I used the HDMI cable. Can the HDMI cable and the coax be used at the same time to connect my DVD/VCR? Any help would be appreciated.