Each registry has its own file with requests.
When you're faced a single @host in a file then it means that the api is not publicly availabe.
In those cases you'll have to run the api on your local machine and execute the call after.
If there are multiple @host lines than it most is publicly available.
Uncomment the @host you want to test and press on the Send Request line above each request.
A new view will pop up and show the results as well as the request, response header and execution time.
More info you can take a look at the rest client extension documentation.