Cannot connect to the internet.--Laptop

My girlfriend's father just bought her the newest mac laptop (I am a dedicated windows user so I know nothing about this thing, plus she isn't exactly computer savvy so bear with me). I tried connecting to my internet using airport and I cannot figure it out. The thing is, the day she was able to use it she connected to their internet at THEIR home, but I can't do it at my home. I tried everything I could think of and resorting to forums has helped me a lot in the past. So, any help is appreciated. Thanks!

Bump, really need help here. I have tried everything I could think of.

What do you mean? Is it generating an error when you try to connect?