Not sure what orca is but from the looks of it all you're trying to do is add the executable to your PATH environment variable. Basically what that does is just adds the full location to your program so you don't have to specify the full location when running commands.
NOTE Only the location of the program has to be added to the PATH. That means you need to exclude the name of the executable itself.
Few things you can do to check it.
From command prompt echo out your full path and check if the path to your orca exe is there -
To set the path from CMD I think you need to use set
It basically means set the path variable to whatever it currently is plus this new thing. Which is what you would want, you almost definitely don't want to override the full path.
For UI version you can open System Properties menu and 'Environment variables' option should be at the bottom. Hit 'Path' variable and select edit and double check if it's there. If not you can add it from here.
Finally to rule out issue with your commands/program - try passing the full location to the command. i.e
Let me know how you get on.