You need to use the Terminal to do it, unless you find an app to do it for you.
1) Find the file you want to hide.
2) Open Terminal.
3) Type this, exactly, without the quotes:
"SetFile -a V " - That last space is important!
4) Drag the file you want to hide into the Terminal window. Your Terminal will add the file path to what you typed, so it should now say something like:
"SetFile -a V /Users/myuser/Desktop/aFile.jpg"
5) Press return. The file will now be hidden.