Usually it can be found by right mouse clicking the app icon > Show Package Contents > system
However you might encounter the below.
"When I show package contents on the Client App theres no system folder."
Yes, on a default normal fw Client app installation this is correct.
In this case, the "system" folder is located in /Users/someuser/Library/Application\ Support/Farmers\ WIFE/system
NOTE: on Mac there are at least two different "Library" locations ... a "system" one and a "user specific" one.
You need to be in the "user specific" one; In Finder > Go > use "alt" key and then use the displayed "user specific Library". If you're on "High Sierra" see e.g. this info here: http://osxdaily.com/2016/12/12/show-user-library-folder-macos-sierra/
So in order to bypass this default path, you simply ensure that the fw Client application is NOT running, use "Show Package Contents" and manually create a folder inside called "system".
Then launch the fw Client app can. Note two things:
a) inside the package inside the "system" folder you now have a fresh new "client.cfg".
b) on the Login window of this fw Client app, note that you now again have the default "Your Server" with IP "127.0.0.1" configuration and you need to enter the server connection details again.
What ever you now configure within this client.cfg will then only be for this fw Client.
IMPORTANT: When you in the future need to manually do a full upgrade of this app, ensure that you first copy the "system" folder ... or at least make backup of the "client.cfg" once your done with configuring it. Because when "replacing" the package, everything is removed!