There are several ways to do it. For example, you can see this IP address in the window properties of the network card of the computer to the network. To reach it open the main menu on the "start" button and in the section "settings" click on the line "Network connections". Open the folder with shortcuts of all established connections, among which you need to find your current and click the right mouse button. In the popup context menu, click "Status" to open the window with information about the connection. It has two tabs - you need the one that says "Support". IP address of the default gateway of this connection placed in the bottom row on this tab.
Another way is to use the ipconfig utility from the set of standard operating system. For this you need to run a terminal command prompt. In the main OS menu there is a line "Run" - click it. This way you will open the dialog box run programs. It is possible to do by pressing hotkeys WIN + R. In the input box type cmd and click OK (or press Enter). So you run the terminal window in which you need to type ipconfig and press Enter. Starts a utility that determines and displays in the terminal window settings for all existing connections of the computer. Will this list and IP address of the default gateway.
However, it is necessary to take into account the fact that when you connect to the Internet not directly but through the router, the main gateway for your computer will be the router. Respectively, obtained by the method described above the IP address will be the IP address for the internal network. To overcome this obstacle it is necessary to connect a cable Internet connection to a network card in your computer directly, or just contact support at your provider with a question about the gateway address.