This is not meant to be a silver soldering tutorial, there are plenty out there and you should get some practice on something that's not a bike frame if it's your first time.
The silver that we used had a 45% silver content and we used about 1.5 troy oz. of it for the frame. We also used Stay Silv flux. I've read to use a flux that can be washed off with water after brazing rather than one that has to be removed mechanically.
One method to practice your soldering is to purchase a few sets of inexpensive lugs. Go through the process of cleaning them up and fitting them to steel tubing of the right diameter. Solder the joints and after they cool hold one tube in a vice and use the other tube to apply a bending moment to the joint. The tube should not break at the joint, but rather along the length of the tubing away from the joint. Also, you can use a hacksaw to cross section the joint and ensure that you have proper silver penetration.