Permanently add to $PATH on MacOS
It depends on the shell you're using. If you use ZSH (the default shell for Catalina and newer systems) you should edit your .zshrc file (see more at https://stackoverflow.com/questions/11530090/adding-a-new-entry-to-the-path-variable-in-zsh).
If you use BASH I would edit both your .bashrc and your .bash_profile files (supplementary information under https://scriptingosx.com/2017/04/about-bash_profile-and-bashrc-on-macos/).