At what angle should I place the bench if I’m doing an incline bench press if I want to develop my upper chest?

45, 60 or 90 degrees?

Technically there is no "upper chest" or "lower chest"…look at an anatomical drawing of your pectoral muscles and everything is connected and contracts all at once.

That being said, 45 degrees is the best angle for incline bench. 90 degrees and you’re not doing bench press anymore (you’ll be sitting upright!)