In the control panel, open the "Network and Sharing Center".
On the left side, choose "Change Adapter Settings".
Choose the right network adapter and double-click on it. If you do not know the right one: First, ignore all with an red X, they are not connected as the second line of the connection info should state. Then check the lower right of the icon. It should be a network cable plug, no bluetooth symbol and no wireless bars.
Click on the details button. Write down/Remember the IPv4 Address, the IPv4 Subnet Mask, the IPv4 Default Gateway and the IPv4 Address DNS Servers. Close the Details again.
Click on the Properties button
Double-click on "Internet Protocol version 4 (TCP/IPv4)"
Change it to "Use the following IP address".
The first three numbers (the network) have to the the same as from the details. The last number is the identifier of this machine in this network. It should not conflict with any other machine and therefore not with the range set in your DHCP server (router). If you do not know your DHCP server settings, choose the number 250. It should not be used.
Enter the IPv4 Subnet Mask, the IPv4 Default Gateway and the IPv4 Address DNS Servers as you have remembered/written.