I'm stuck at the following steps as I cannot see app or mail config files anywhere in the zip I downloaded...

STEP 4b. (OPTIONAL) MODIFY "app.config" FILE:

By default YAF is designed to be installed at the root application on any IIS web server. If you want YAF to be installed off of the main root in a sub folder, you need to modify the root key. Make sure the files in the /bin directory of the YAF zip file are copied to /bin directory on the root of your web server. Then open up "app.config" and uncomment the YAF.AppRoot key. Enter the value as the  directory to your forum. Example: If you have install the forum in the directory "/forum/yaf/" you will need to uncomment/add key with name YAF.AppRoot and value "/forum/yaf/" to app.config.

STEP 4c. MODIFY "mail.config" FILE:

Modify the SMTP settings by entering your mail server information.

Getting this error:

Could not load file or assembly 'Microsoft.Bcl.AsyncInterfaces, Version=1.0.0.0, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)

And then in the stack trace...

[FileLoadException: Could not load file or assembly 'Microsoft.Bcl.AsyncInterfaces, Version=1.0.0.0, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)]

[FileLoadException: Could not load file or assembly 'Microsoft.Bcl.AsyncInterfaces, Version=5.0.0.0, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)] YAF.Core.Context.YafHttpApplication.Session_Start(Object sender, EventArgs e) +0 System.Web.SessionState.SessionStateModule.CompleteAcquireState() +375 System.Web.SessionState.SessionStateModule.BeginAcquireState(Object source, EventArgs e, AsyncCallback cb, Object extraData) +1257 System.Web.AsyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +703 System.Web.HttpApplication.ExecuteStepImpl(IExecutionStep step) +75 System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +158

The following dependent assembly entry...

  <dependentAssembly>
        <assemblyIdentity name="Microsoft.Bcl.AsyncInterfaces" publicKeyToken="cc7b13ffcd2ddd51"/>
        <bindingRedirect oldVersion="0.0.0.0-5.0.0.0" newVersion="5.0.0.0"/>
      </dependentAssembly> 

should be

  <dependentAssembly>
        <assemblyIdentity name="Microsoft.Bcl.AsyncInterfaces" publicKeyToken="cc7b13ffcd2ddd51"/>
        <bindingRedirect oldVersion="0.0.0.0-6.0.0.0" newVersion="6.0.0.0"/>
      </dependentAssembly>