brew install indigo-dc/oidc-agent/<formula>
i.e.
brew install indigo-dc/oidc-agent/oidc-agent
Or brew tap indigo-dc/oidc-agent and then brew install <formula>, i.e.
brew tap indigo-dc/oidc-agent
brew install oidc-agent
brew help, man brew or check Homebrew's documentation.