First question...why am I doing back and biceps on the same day? I'll tell you why. Much like your chest and triceps, your biceps are a secondary muscle of your back. It is inevitable that you're going to work your biceps when you're lifting back, so it makes sense to train them on the same day. Also, as a beginner you shouldn't be lifting more than 4 days per week...your body needs to recover. With that being said, here is an example of a beginner back and bicep workout.

-Seated Cable Row:
This is a common back exercise. One of the first that I learned, and I still love it. This is done on the cable machine..same one used for tricep pull downs. Set the weight low enough to do 12 comfortably for the first set. Aim for 3 sets of 10 reps. Check YouTube for a demonstration of proper form.

-Lat Pulldown:
This exercise works your lat muscles, which are the muscles that extend over your mid back and upper ribs. This is also a common exercise that can be done several different ways. I recommend doing lat pulldowns while in a seated position pulling the bar down to your upper chest. Same rules apply...3 sets of 10 starting out light. Check YouTube for form.

-Back Extension:
Think the opposite of a sit up. These work your lower back. There are several apparatuses that back extensions can be done on, but your gym likely has a specific back extension set up. Do these without weight to begin with, and aim to do 3 sets of 10. YouTube has several demonstrations.

-Bicep EZ Bar Curl:
The curl is the basis for pretty much all bicep workouts. I recommend using the EZ bar/curl bar. It is curved in the middle to put your hands and wrists in a comfortable position. You can either do this close grip or wide grip, they each hit different parts of the bicep. I prefer doing 2 sets close grip, 2 sets wide grip...but do whatever is comfortable for you.

-Concentration Curl:
This is a great exercise that really focuses on your bicep. The name is fitting, as you immobilize every other part of your body besides your bicep. All you need is 1 dumbbell and I highly recommend starting at a real low weight for this one until the form is perfect. Once again, check YouTube for proper technique.