Slow wifi vs fast ethernet

Hello everybody, I am kind of a newbie, so I need some help in what to do. I just upgraded my interent and it is 200 mbps down and 10 mbps up (I know thats not the fastest, but hey it matters). I have a stand alone modem and when I connect my ethernet cable from the modem to my laptop, I do get 200 mbps down.

When I connect the router to the modem and then connect my ethernet cable from my laptop to the router, I still get the 200 mbps down. No issues so far.

The problem is the wireless wifi from the router, it is only 25 mbps, and that is the speed from my previous service. How can I fix this to go faster?

My router is the N900 802.11 Dual Band Gigabit, Model WNDR4500. It literally says on the box at least 450-500 mbps- up to 900mbps. I am only needing 200. 

So guys, what do I do? Is it the channel, the mode, what do I look for and change in the genie admin? Thanks!