Open up your ~/.bash_profile don’t worry if it doesnt exist already, just make it.

browser_stack(){
	java -jar ~/Downloads/BrowserStackTunnel.jar FEnE97YWyQEqa2MnMIHm $@,80,0;
}

Copy and paste the above line in the file and save.

Open terminal force a reload of your profile with the following and run the command like so:

. ~/.profile && . ~/.bash_profile

Then run:

browser_stack local_domain