@Trisha - I'm sure 9k will point you in the right direction. However, I'm a little curious as to why you'd want to do this unless you don't have a data plan, don't have a wifi connection at home, and want to install and/or update software on your n900.

If that's the case though, I'd recommend just biting the bullet and getting a wifi router. They are cheap and don't really fall out of date very quickly. It's a good investment that'll let you use your n900 around the house, keeping you untethered to your computer if you don't need the extra functionality it provides.