Connections and principial bundles

Question

I'm more or less familiar with the concept of connection of the vetor bundle: given vector bundle $E$ there is a canonical construction of so called frame bundle (which is principial bundle) $F(E)$ and conversely once we have a principial bundle we can construct vector bundle from it via the so called associated bundle construction. However when it comes to connections, I'm only familiar with this concept in vector bundle case. I would like to learn basics from connection theory for principial bundles. Therefore I would be grateful if somebody could give me some good reference for this topic.