If you only have a set of speakers and a DVD player with no speaker terminals on it you would need a surround sound receiver that would connect to the TV.
If you have a home theater in a box so that the "DVD" is really a DVD/Surround receiver then you would connect that to the TV in two ways. One is for playback of the DVD. The other is to get the TV sound into the HTiB so you can get better sound for other sources. The type of connections you use will depend on the exact ones on the TV and HTiB.