Acer aspire e14 laptop won't connect to wifi

Hello, I have an Acer Aspire e14 that I got yesterday, which worked ok at first, but when my dad tried to hook it up to wireless internet access it kept saying incorrect key or password, and when he finally got it up using a different wifi, it connected, but I can't access the internet, even when I put back the internet adapter cable, it doesn't work.I need my laptop for school, since I'm doing programming, and I need it to use at school as well. Can some one please help me.