adding a reference. how do i ?

Question

hi i am a newbie to .net. how should i rectify this error. please help me.
 
Error : The type 'MSCommLib.HandshakeConstants' is defined in an assembly that is not referenced. You must add a reference to assembly 'Interop.MSCommLib, Version=1.1.0.0, Culture=neutral, PublicKeyToken=null'. C:\Program Files\Microsoft.NET\code\PTZControlPort\PTZControlPort\ViscaPTZCommand.cs 281 5 PTZControlPort