Remote Debugging

Hi

I have set up a project in Pycharm with mapping to a remote server.  I set up one file in the project and managed to get this working with minimal problems.  It runs and debugs from the remote server correctly.  I next added a new file to the project.  When I try to run or debug this it runs the local file not the remote one (even though this has been uploaded to the remote server).  When I try to add a mapping to Run/Debug configuration for that file there is no 'Path Mapping' Box present.  How do I fix this?