Web Service Help

I am an old dog trying to learn new tricks. I need to create a web service on an SQL Anywhere 16 database and call it from a Powerbuilder 10.5.1. Build 6021 application. Since I have never done this, I am having a hard time trying to create this process. Where I'm stuck is I created a web service and now I'm trying to create a proxy on the application but it asks for a WSDL file and I have no idea how that is created. Any help will be appreciated.

Rick