A maneira mais comum é adicionar o comando ao arquivo .bash_profile em seu diretório pessoal.
Citando man bash , que também lista outras opções:
When bash is invoked as an interactive login shell, or as a non-interactive shell with the
--loginoption, it first reads and executes commands from the file/etc/profile, if that file exists. After reading that file, it looks for~/.bash_profile,~/.bash_login, and~/.profile, in that order, and reads and executes commands from the first one that exists and is readable.