Newbie to ASP.NET Longtime VB6 Programmer

I do not want to place code in HTML but Rather in WebForm .net code. How do you reference another page.

Say I am Login.aspx webform and I click a button. I want to send them to a welcome page called test.aspx.

How do I write the code in .net Design and not HTML??

Also, Is it better to code in HTML or .NET in a webform??