Upload file via AppleScript

[Capital]

I can't understand, how to create AppleScript automation for active (opened) Cyberduck window.
In example files we have lines:

tell application "Cyberduck"
set theBrowser to (make new browser)
tell (theBrowser)
....

How can I set theBrowser to active opened and connected window? Something like this:

tell application "Cyberduck"
set theBrowser to (GET ACTIVE browser)

Is it possible? Thx.