Contol Knobs (No Response)

Hello, I am new to the group and this is my first attempt to post so please bare with me if I make an error…thank you.
I have a question regarding the output knobs on the front of the UR12 Interface I purchased the other day.
My wife was planning on using it with my computer (Windows 8) to do a little recording, but when I was unable to adjust sound on both the Mic and The Headset I disconnected and boxed it up to bring back where we purchased.
I did install it into my PC using the USB cable and I do believe (I hope) it was done correctly because I tested the Mic and it worked and the Headset worked fine. Once I did plug in I lost the use of my PC speakers, not sure if that makes a difference? Not sure if it has anything to do with the issue, but on the front of the box there are 2 Red lights and 1 White light, the White light stays lit, 1 Red light stays lit but the second light would come on and go right off.
Sorry this is so drawn out, just wanted to try and explain even small details if it may help.
Have I missed something when installing that’s preventing the adjustment knobs to operate? Thank you!