Macbook Pro can't find wifi

Hi, I just bought late 2011 Macbook Pro 13", and I have a problem with Wifi connect.

First of all, my Mac finds all neighboars wifi except mine.Also, I can connect to my wifi with my sisters Asus and my iphone. Can anyone help me to solve this problem?

(By the way, I'm new on Macs, so it would be great to explain step by step)