You're using Cadence schematic tool and do your design by picking and placing transistors, e.g.: https://www.youtube.com/watch?v=LJ4xeZgChUA.

See this article

You have to have the specifications of the circuit to be designed. You may make a manual design for the circuit by estimating its most important parameters. Then inter the circuit to the circuit analyzer of the CAD tool, Spice for example or an alternative of it. You can start with a published design. For the schematic circuit design example please see the attached link:http://www.ee.columbia.edu/~kinget/EE6350_S14/PPG6350_Web/SystemOverview.html

The comparator is a high gain differential amplifiers as seen in the comparator circuit. After making your circuit design by determining the W/L ratio of all transistors in the circuit you make the simulation using spice to verify the required performance parameters of the comparator such as the low frequency gain, the input impedance, the output impedance.

Then after satisfactory design you can make physical layout.

After successful layout you can make post lay out simulation after parameter extraction.

If your circuit post lay out passes the specs and requirements, you can send your design to the factory for fabrication.

Best wishes

there are many comparator topologies in literature. most of them are implemented using two inverters connected in what is called negative feedback mode to increase the difference between the two input signals.

of course first the difference is amplified before the input goes to the negative feedback inverters.

here is a good example for a novel comparator you can use

Article A new CMOS comparator robust to process and temperature vari...

This document might be helpful as well

http://webpages.eng.wayne.edu/cadence/ECE7570/doc/comparator.pdf