If you're talking about assigning a static IP address to your system, you can do that through the network and sharing center. If you just need a different IP, click start, (Right click if you're running Windows 8.1 or 10) and type cmd in the search box. (On Windows 8 and 10, there will be an option called "Command Prompt Admin" this is the option you'll want if you're running Windows 8 or 10.) On Windows Vista and 7, right click on the cmd option and click "Run as Administrator". Click yes at the UAC prompt. In the command prompt, type the following commands, pressing enter after each one:
ipconfig /release
ipconfig /renew
You may have to reboot after this.
If you want a static IP, right click on your network icon in the notification area and click "Open Network and Sharing Center". On the side pane, click on "Change Adapter Settings". Right click on the active network adapter that reports internet access and a window will appear. Click on the IPv4 (Internet Protocol Version 4) option in the box with all sorts of options. Choose the option to obtain an IP address and DNS manually. In the IP field, enter a valid, unused IP address. It cannot end in 1 or 255 and must match the IP class that your ISP uses. (To find this out, open command prompt and type ipconfig. The prefix for your IP address will, most likely, begin with 192.168.1.XXX.) The first three boxes must match the current IP address. The last box can be any number between 2 and 254. The subnet mask field will be filled in for you when you click into it after inputting a new IP address. The default gateway must also match what is displayed in the command prompt. If you cannot see the default gateway, type ipconfig /all to see a list of all of the adapters and configuration information. As for the primary DNS, enter 8.8.8.8 for the primary and 8.8.4.4 for the alternate. This is Google's public DNS server.
Click OK twice to commit your changes. If you get a limited status, verify that the IP address is not already in use and that it matches the class that your ISP uses.
Hope this helps.