how do i track my stolen iphone that is without an active 'find my iphone' app?

You cannot. FindMy must be active, the device powered on, and the phone must be on a network.

Here's what to do next. https://support.apple.com/en-us/HT201472

Just the old-fashioned way. Look around for it.

I'd lock the device and put it in lost mode as per the instructions.

If find my iphone is off it is unfortunately not possible to track it