2006 Chevy SSR

Hi I am finally coming back from the mayo clinic today. I am sitting in the car and a thought came to my head. How do you fill the new radiators up. I saw on my dads truck that their is no radiator cap. My uncle told me if the radiator ever goes that you have to jack the truck up on the passenger side almost to where it looks like it is going to tip over and that is how you fill it up. Do you fill the new cars up through the resivore. He told me a friend of his had to change the radiator out and it kept over heating after he changed the radiator. My uncle contacted a mechanic and this is what the mechanic told him to do. Is this true. Thanks for your time and help.