This code enables you to display a login form anywhere in any theme.
You can add the code directly to a login page template.
You can hook the login form using a custom function and conditional tag.
This post includes the code which also creates a Genesis page template that includes all the parameters you can modify to customise the form if needed.
The page template also displays the login form and removes the content for logged out users. Once logged in, the template displays the full content.