How use .xsd file in WCF service?

I need to develop WCF service that receive XML from client and process it. I wrote the service and I get the XML as s string something like:

 [DataContract]
public class TransferData
{
    [DataMember]
    public string xml;
}

But they gave me .xsd file. I am not sure what is this file and how I can use it in WCF service?