There is nothing special to be done. Just type in the command you want to run:
curl https://example.com
The only thing you have to make sure, is that curl is installed.
If you run n8n via npm, you have to install it on the host directly.
If you run it via docker, you have to create your own docker-image which extends the base image and installs curl.
Here a previous topic which talks exactly about that: