How to recover file missing?

[LastSystem]

Hi !

by mistake, I deleted a file
How to recover file missing?

I have backup and I have the file, but I can not seem to put the same one I had before

What steps would be the correct ones?

[LastSystem]

I found the solution :

Go to "Set Source File...." and enter the file

In the saved project, ...you should first see what file was
You must close the project and open the old one