You have to check: focal distance, focal region, near transition, far transition (all set to 0), near blur, far blur (set to whatever >0).
Select Gaussian DOF to have a nice regular blur.
Check unbound too, so you don’t have to walk in to see the effect.
Set your postprocess material to “aftertonemapping”.
For the rest, I don’t know. It should work.
Something to dig, for sure.