To make calls to REST API of the Juice Shop via a comfortable UI you may use Postman.
Follow the setup instructions on https://www.postman.com/downloads.
If you are more used to make calls to REST API of the Juice Shop via command line you may try Httpie.
Follow the setup instructions on https://httpie.org.
If you are more used to make calls to REST API of the Juice Shop via command line you also may try the classic Curl.
Follow the setup instructions on https://curl.haxx.se.