Is my bike too big for me?
If you cannot comfortably straddle the bike with your feet on the ground it is too big. The bike you have appears to have a nearly horizontal toptube.  As others have said try to return it or at least exchange it for a model that feels comfortable. A model with a slightly sloped top tube may give you a better fit. Don't make your decision based on the stated frame size. Test ride the bike (or several) before making your final choice.