How does register the file extension in vdproj,so that it will automatically open in the concern application

Question

I need to register the file extension in vdproj,so that when setup is installed by someone the file is opens into registered extension.

Say for example if my program exe is able to read text file with extension of .tet, so when i create any text file with extension .tet like sample.tet ,it should be open into my program exe not notepad.

Please suggest how to do that.