SOAP API and SOAP UI and Authentication Issue (20014)

We are trying to use "getMObjects" SOAP API function in SOAP UI and we are always getting the "20014 - Authentication failed" error in our response bac.

Can i get a help on how to test SOAP API's  and how to provide the correct header parameters,

(i have placed the Marketo ID (from the Webservice SOAP screen) , encryption key (from the Webservice SOAP screen) and timestamp in WSDL format)