I think you need to use biterscripting commands for IS (Internet Session) like this. (To POST to a page, you need to use the 'ispost' command. To GET a page, you can just use the 'cat' command.)
# Declare variables
var str page
# Start internet session, named s, user agent Mozilla.
isstart s "" "Mozilla/5.0"
# If the site is https://www.abc.def, connect to site.
isconnect s "https://www.abc.def" > $page
# The site's index page is in variable $page.
# Suppose the login form is in this format -
# <form name="login" action="login.php" method="post">
# Account: <input type="text" name="login"><
# Password: <input type="password" name="pswd">
# <input type="submit" value="submit">
# </form>
# Login by posting "login=me&pswd=mypassword&submit=submit" to login.php.
ispost s "login.php" "login=me&pswd=mypassword&submit=submit" > $page
# "me" and "mypassword" are values of login and password.
The page after the login is now in variable $page. I thought this is the page you are looking for.
Hope this helps.