export PATH=$PATH:<Path-to-folder-you-want-to-add>
The easiest way to add a new path to $PATH (the environment variable) is with the export command. In this example we’ll add “~/opt/bin” to the user PATH with export:
export PATH=$PATH:~/opt/bin
You can run that directly from the command line, then check the $PATH with echo to show that it has been added like so:
echo $PATH
sudo nano /etc/paths
https://www.architectryan.com/2012/10/02/add-to-the-path-on-mac-os-x-mountain-lion/