Click on Start, then click on Run.. Type cmd or command in the text box. Click OK.. Type net send for the first part of the command string. Press Space, then type the username or domain of another computer in the network.Press Space, then type in your message. Hit Enter to send the message to the designated computer.lick on Start, then click on Run.. Type cmd or command in the text box. Click OK.. Type net send for the first part of the command string. Press Space, then type the username or domain of another computer in the network.