I am installing a new bathroom fixture. There are 4 black wires and 4 white (including the ones coming from the fixture), the plug now works and the light doesn't. My question is do all the wires go together or should there only be 2 white and 2 black for the light and 2 and 2 for the plug?

You hgave had 19readers and no answers because your description lacks detail. What are you installing, don't just say fixture because that could be a light, fan, whirl pool, etc... The balacks and the whites, are they in the ceilig box and how many come from the "fixture" What plugs, where is it and is it connected to a switch or not. Back to you for more info