Once you've loaded the URL that you want to submit the form on you can use the below to fill in all the required fields and then click submit.

VB Code:
  1. 'WB1 = Webbrowser control
  2. WB1.Document.All("username").Value = "Test" 'enter Test into username field
  3. WB1.Document.All("password").Value = "test" 'add test into password field
  4.  
  5. WB1.Document.getElementById("Submit").Click 'sumbit the form