The bummzack's answer is right and technically the good one.
But I will add this answer to encourage you and anybody else to try changing your point of view every time you encounter a problem. Too much often, peoples (including me indeed) doesn't step back (in their mind ^^) to have a better view of the problem.
Here is a very simple example; if you can't link the legs to the torso because you can't (in fact you can as Bummzack said) or don't know how to link them, step back and try step forward another way: can you construct you model from another bone?
I don't know if you tried, but obviously yes you can if you start from the head.
This skeleton isn't perfect nor it does necessary fits your animations needs (I didn't rotated bones the right way etc...) but that's just a bone linking example and I'm a Blender Rookie too, so I might be wrong. But the important idea is that we need to try others perspective when encountering a problem.