Hi Pulkit,
I don't think Reltio exposes the data via SOAP. Hence there is no WSDL exposed here. In this case you cannot import all the API's to SOAP UI directly.
Please have a look at the Reltio's REST API interface here -
https://docs.reltio.com/restapis/aboutrestapi.html .
You can configure the API's in any external tool like Postman , SOAP UI etc. I'm not sure if we have entire collection exposed from Reltio.
You can also take a look at the Developer portal -
https://developer.reltio.com/index.htm and it has a good Swagger UI.