How do I view my DVD/VCR player after being hooked up to Zenith Converter box?

I successfully hooked up my og TV set with the Zenith Converter box. My TV with HD viewing is marvelous. However, I cannot watch any DVDs or Videos. For some reason it just won't work. What do I need to do so that I can use my DVD/VCR player? Any help is greatly appreciated. Thank you.