How do I hookup a laptop computer to the internet?

I just purchased a laptop computer that has a wireless card. My sister has a desktop computer in the house and she is hooked up to the internet by a dial up connection, not high speed or cable. A phone line plugs into the back of her compter and the dail up connection goes thru Net Zero for access. How do I gain access to the internet also for my laptop that has a wireless card. My sister is willing to change her setup if she needs to so we both have access to the internet but we don't know what to do.I think we need a router( wireless??) but not really sure how to hook it up and do we more than just a router. There are lots of routers in the stores, what's the difference.Unfortunately we are both very computer illterate when it comes to tecnicle stuff so it is very hard to ask the proper questions and understand the answers. I would appreciate anyone that would have the patience to give an answer in very simple steps that even a slow witted computer user like me can understand.