Am new to studio lighting myself, but if you only have the two lights, you will need to light the BG with one and the subject with the other, dependig on the umbreala type will decide on how you use them, if they are shoot through i.e. translusant like a soft box, then you would point the rear of the umbrealla at he BG/Subject, if the are reflective, you point the light away from the BG/Subject, hope that makes sense.