getting started with SOAPUI

i have an intranet application i am trying to authenticate against.
i get a credentials failed message.
Can someone on this board help me get started?
i can view the WSDL in IE.
i am new to WSDL...but i have been trying to authenticate for the past few days and have had no luck.
i have access to all .xsd/WSDL.... i can post anything i need to this forum...i just need some direction.
i even have access to tech support for this third party application that i need to gain access to.

how would i get started?