How to host WCF if contracts,implementation and host are separate assembly

I have downloaded a layered sample from Codeplex from this link: https://layersample.codeplex.com/releases/view/107797

This contain a WCF service with this structure:

1. service contract library
2. service implementation library
3. web host project

Question: in the web host project, there is no .SVC file and it only contains configuration in the web.config file.

Can anyone guide me how it works or how I could consume/add service reference in a client application/how to host this on IIS.

This is the web.config file :

<system.serviceModel>
    <serviceHostingEnvironment multipleSiteBindingsEnabled="true">
        <serviceActivations>
            <add factory="System.ServiceModel.Activation.ServiceHostFactory" 
                 relativeAddress="./LeaveService.svc" 
                 service="LeaveSample.Services.LeaveService" />
            <add factory="System.ServiceModel.Activities.Activation.WorkflowServiceHostFactory" 
                 relativeAddress="./LeaveWorkflowService.svc" 
                 service="LeaveSample.Workflows.LeaveWorkflowService" />
        </serviceActivations>
    </serviceHostingEnvironment>
    <services>
       <service name="LeaveSample.Services.LeaveService"   
                behaviorConfiguration="DefaultServiceBehavior">
          <endpoint name="basicHttpLeaveService" 
              address="" 
              binding="basicHttpBinding" 
              contract="LeaveSample.Services.Contracts.ILeaveService" />
          <endpoint 
              address="mex" binding="mexHttpBinding" contract="IMetadataExchange" />
       </service>
       <service name="LeaveWorkflowService">
          <endpoint name="basicHttpWorkflowService" 
              address="" 
              binding="basicHttpBinding" 
              contract="ILeaveWorkflowService" />
          <endpoint 
              address="mex" binding="mexHttpBinding" contract="IMetadataExchange" />
       </service>
    </services>
    <behaviors>
       <serviceBehaviors>
          <behavior name="DefaultServiceBehavior">
              <serviceMetadata httpGetEnabled="true" />
              <serviceDebug includeExceptionDetailInFaults="true" />
          </behavior>

          <behavior name="">
             <serviceMetadata httpGetEnabled="true" />
             <serviceDebug includeExceptionDetailInFaults="true" />
             <sqlWorkflowInstanceStore connectionStringName="workflowStore" 
                    hostLockRenewalPeriod="00:00:30"
                    runnableInstancesDetectionPeriod="00:00:05" 
                    instanceCompletionAction="DeleteAll" 
                    instanceLockedExceptionAction="AggressiveRetry" 
                    instanceEncodingOption="GZip" />
             <workflowUnhandledException action="Cancel"/>
             <dataContractSerializer maxItemsInObjectGraph="2147483647" />
         </behavior>
       </serviceBehaviors>
    </behaviors>
    <extensions>
       <behaviorExtensions></behaviorExtensions>
    </extensions>
    <tracking>
        <profiles></profiles>
    </tracking>
</system.serviceModel>

Thank you

The project you downloaded is using "fileless activation":

<serviceActivations>
  <add factory="System.ServiceModel.Activation.ServiceHostFactory" 
       relativeAddress="./LeaveService.svc" 
       service="LeaveSample.Services.LeaveService" />
  <add factory="System.ServiceModel.Activities.Activation.WorkflowServiceHostFactory" 
       relativeAddress="./LeaveWorkflowService.svc" 
       service="LeaveSample.Workflows.LeaveWorkflowService" />
</serviceActivations>

The above portion of the configuration file defines two service activation endpoints, without having to have a physical .svc file.

It is hosted and consumed like any other WCF service using IIS - the only difference is there is no .svc file.

File-less activation was one of several WCF features introduced with WCF 4.0. You can read about it (and the other features) here - A Developer's Introduction to to Windows Communication Foundation 4.