Running test CPC

Im training for my CPC, specifically the running test at the moment. However I’m struggling with it, does anyone have any advice I can follow for going from absolutely no running at all to where I’m at now, and how to progress further?

I’ve just tried interval running with 400m with 6 reps. However could only do about 3 until my body told me it was finished.

I currently have a quickest time of: