WSDL: A WSDL is an XML document that describes a web service. It actually stands for Web Services Definition Language.
The URI is the link to your API.
In your SOAP UI,
Ð¡lick on the main toolbar or select File > New Rest Project
It will ask you for the link. That's where you should put your API link.
If you are provided with WSDL then you can use it. Otherwise, it is fine.
Let us know your findings.