If you want it to work only once you can run this command in your terminal
$ export PATH="$HOME/.composer/vendor/bin:$PATH"
But if you want it to be stored and work whenever you open a new terminal you need to do the following steps:
1) open the ~/.zshrc file by running the following command $ nano ~/.zshrc
2) at the bottom of that file add this export PATH="$HOME/.composer/vendor/bin:$PATH"
then to save hit (ctrl + x) then (Y) then finally hit enter(or return).