Error when I add a new file using 'sd add' in source depot

I tried to add a new file using

sd add myfile.txt

But I get this error saying

myfile.txt - file(s) not in client view.

Can you please tell me how can I fix it?

The general answer is that you need to edit the client view and/or root ("sd client") so that your local "myfile.txt" is mapped to the depot.

For a more specific answer I'd need to know:

1. The full local path of myfile.txt
2. The full depot path you want to add it to