I has some important filesthat I want no one could read or delete them. But I don't know to to add those properties to them. If you know the answer, please reply me.

Hello khogdaubang

and welcome at GSFs.
When running a Windows operating system please

1. locate your file you want to set Read-Only and mark it
2. right mouse click
3. check up the box Read Only on the General tab
4. Checking the box hidden at attributes hides this file

But why don't you make a backup of that file(s) if it's so important?

Regards
B. Udo