How do I update from watch os 5.3.9 to the latest watch os 7? I have a 3 series watch and my phone runs iOS 14.

How do I update from watch os 5.3.9 to the latest watch os 7? I have a 3 series watch and my phone runs iOS 14. The watch app keeps saying my watch os is up to date, but clearly 5.3.9 is not the latest. Just switched iphones as well, but unpaired my old iPhone from my watch before doing so.