Please make sure to install homebrew before you install Steward.
The following command will take care of everything for you. It will download the latest executable to /usr/local/bin and apply the executable permissions with chmod +x /usr/local/bin/stew. It will finish with the command stew boot and ask you if you want to install the dependencies if they seem absent.
bash <(curl -s https://stew.sh/install)
Afterwards, you can run the following to verify that everything is working correctly.
Install and boot the stack
Steward can install, (re)boot and update all services with a single command. It doesn't modify any configuration files and maintains compatibility with the default homebrew setup for php.
When everything is OK, you will see a similar output as below.