IP Core
if you purchase an ip core, you don't lay it out yourself. you instead draw an empty box in your layout and put your connections at the requested locations (VIN = -22, 30, Enable input = -100, 30)
Then the IP is added to your GDS database by the fab for example and your chip is fabricated. When you get it back there's an ADC in it and everything works as expected.
The IP manufacturer usually gives you some macro model for simulation, and you don't get the layout or the full schematic. You just work with the macro model, and leave them a space in the GDS file and they finish assembling the GDS before fabrication.