I downloaded a mod onto my hard wat do i do after that
What about... telling us what kind of mod you're talking about? Or even better - the name of the mod itself? Or reading the ReadMe which is most likely attached to the mod?
How should we be able to help you if you're not giving us any information?
@rohitmz Go through this tutorial:
Don't rush through them, otherwise you're going to end up in a mess.