Using WSDL for frontend website login

I'm building a website for a company that wants me to use their internal database of users for frontend website login. They provided me with this:

http://ift.tt/1pFTeZV

How do I start using those methods? Or where should I start learning this? This is all totally new. I'd normally do this using PHP and a database of users in mySQL. How do I do this? Thank you