Howe initially signed Kelly for former club Bournemouth.
The defender told Newcastle's website: "It’s a good feeling. I think when you've got people that you know already, it kind of makes you feel a little bit more settled and at ease. I know some of the players and of course the manager, the gaffer.
"So I think in that sense it's a nice feeling to kind of go into a new place, but at the same time you kind of get that feeling that you're kind of home at the same time, you know?
"But for me to come here, speaking to the gaffer, I mean, I didn't really need to take much.
"The gaffer knows how highly I think of him and the way he kind of shapes his teams and wants his teams to play, I think it kind of suits my attributes. So it kind of just made sense."