Your IP is assigned by your ISP So if you want to change your IP then you need to contact your ISP or use a different ISP.

You can use a proxy to change your IP address. I've been using a product from a software called Private Proxy. The software will provide you with 4 different servers, 3 in the US and 1 in the Netherlands. When you are logged in with this proxy, your real IP address will be completely hidden. Their product works great and they have excellent customer support, so they'll be able to help you out with any questions that you have. Below is a link to their website. They have instructions that are pretty detailed, so you shouldn't have any issues. http://www.privateproxysoftware.com