This is how I do it. In my web service method I provide parameters like this:
Public Function UpdateCategory(ByVal Description As String, ByVal Active As Boolean, ByVal CatID As Integer) As Boolean
There are two ways to submit via Web Service: InfoPath Data Connections Or Managed Code (Visual Studio)...
If using InfoPath Data Connections you Add your Web Service as a Submit Data Type. You map your Web Service Method parameters to the Form Template Main Data Source fields. Then you can add a button on the form and give it a Submit Action with the Data Connection you just created.
If you are using Managed Code you can do something like this in a Button Submit_OnClick event (VB.NET):
Try
Dim ws as New YourWebService.Service
ws.URL = getCurrentServiceEnvironment() 'a function
ws.Credentials = getUserCredentials() 'a function
ws.UpdateCategory(strDescription, blnActive, intCatID)
Catch ex as exception
'exception error handler here
End Try
That's it in a nutshell. If you need further examples let us know and we can point you to some better documentation than mine here in this forum.