How to attach a potentiometer to a servo motor shaft

I may need to pick out a Servo motor first. I found a couple of hours, they look simple enough to build. But all of the servo Motors on Amazon seem to be for little plastic robots. I need something big

Have you considered posting a description of you project with enough details for someone to pick out a servo motor or do want to do that yourself ?

I know they often come with POs built in

POs ?

What is that ?