Contact your provider. Big cable?DSL providers, like Road Runner and Optimum Online have a feature for people with more than 1 PC. You can purchase an additional IP address for the other computer for an extra $5 a month. Then you can buy a small hub to connect them both to the internet.
If they will not do this, you will probably need to split the connection using a router. If you go for the hub/router, I suggest Linksys brand. Check
http://www.pricewatch.com for good pricing.