When you add the file to the Miscellaneous Files in the project properties, the file is included in the deployment package. It will be in the extract directory on the machine once the deployment package is extracted. Once you create your deployment package, you can rename the .OpenSpan file to .Zip and open it to see your file in there.
Here's a simple way to get to the folder where the files are extracted to at Runtime. You need to add a Static method from the OpenSpan.Runtime.Core.dll to get the GetProjectPath method (right-click in the Toolbox and select Choose Items, then select the Pega Robotics Static Members tab and select From Directory Location). If you are using an older version of Studio without the FileUtils, you can use the Static method from the GAC Path.GetDirectoryName (right-click in the Toolbox and select Choose Items, then select the Pega Robotics Static Members tab and select From Global Assembly Cache, select the mscorlib assembly and locate the method).