The hard drive should be screwed from the sides not from the back like an SSD. Mechanical hard drive from the sides, SSD from the back or side.
Flip the hard drive so it's sideways, lable facing up, controller circuit board or metal/plastic cover facing down. Screw it from the sides on the left and right hand side of the case. It will sit right in front of the fan and get some cooling.
Currently you have it with the label sideways like an SSD. It should be with label facing up and connectors facing the back of the case towards the inside opposite side as the fan. Jam it in the holder and it will be a tight or just loose fit. The screw holes on the hard drive will line up with the holes on the right and left side of the case. You should be able to get 4 screws in there. AS long as the hard doesn't touch the fan you'll be fine. It can even be 1/2mm away and scrapping the fan....as long as it doesn't stop the fan from spinning. We actually always purposely choose a slot in front of a fan for mounting a hard drive to give it some cooling.
Read the manual for the case and it'll tell you the exact position and location to mount a 3.5" drive. It could be rotated 90 degrees form a conventional case.