Upvc door frame help

[JLM1978]

Hello I've been trying to weather proof my front door and have had advice to fit a threshold kit. I have now purchased it but I'm not sure it should go in to a upvc door frame? Does anyone know if anything should sit in the bottom of the door frame? Picture for info but not mine.
I was actually looking for a L shaped cill / sill cover for the concrete threshold under the upvc door and ended up with this issue and still havent got the cill cover!
Thanks in advance.

 

[Notch7]

I doubt if a threshold will work

does the door frame have no external cill -that projects over the brickwork?

have you checked if the drainage holes are blocked

is the water getting underneath the door frame

if the door was fitted without a cill, one cant be added now because it would add 30mm to the door frame height

a pic from outside would be helpful -one showing the bottom half of the door and below it