I can't receive internet on my laptop

Hello,
I bought my Dell Inspiron about 4 days, and I tried to get on the internet; however, I can't. See, I have a desktop and I thought that I could use my dial up from that and plug it in the laptop. However, it didn't quite work out that way. For example, everytime I try to connect, it says "failed to find connection" and I've tried everything. I even tried to use wireless even though I don't have it. I would really appreciate if you can help me, because if I have to take it back to the store then I will. Also, my modem works well, because I can use my modem for my desktop, and it allows me to get on the internet anytime. I would really appreciate if you would help me... Thank you in advance.... :)