How do I fix my wifi?

I’ve had problems for 5 days already with my internet, today I’ve fixed it. It was all a IP and DNS server problem, so now I can go on the internet but only via my computer. I can’t connect to the internet via wifi from my laptop. How do I fix this problem? What is wrong with it? On my laptop where I go to the two little computer screens in the taskbar I clicked it and go to Network and Sharing Center, I see the laptop name then the modem icon and name following by the earth this the internet. Between the modem and the earth/world there’s a red X mark.

I don’t know why my laptop won’t connect to the wifi from my modem but the computer is going on the internet via the modem thus the ethernet line.

So how do I fix this? Help please.