Hi Aidy
im not an expert at all, but if you have a plain background thats white, then light that upseperately(lightshining on the wall directly)that will bleach it out and leave the subjects in an uncluttered foreground, if its a coloured background then you want to bounce the flash as well as use a reflector to get the light under the faces as well as directly onto them. Bounce the flash with a piece of white card infront of the flash angled up at the ceiling, experiment and see what you can do!