How do I initiate sex with my new girlfriend best?

So I have recently asked this girl I've been dating to be my girlfriend and she said yes. It has been a few weeks and I think the time is right to make a move (inaction can be as bad as too soon I'm told). However, I'm at a loss for the best way to initiate. Obviously I don't want to just say "do you want to have sex" as that implies a lack of confidence. But I want to be sure she is into it. I don't want to risk confusing flirting with sexual desire. Should I simply tell her I want her?