The Preferences window opens to Account tab selected from the sidebar on left by default.
Open the Steam application, select from the menu bar at the top, Steam->Preferences. (IF YOU JUST NEED TO KNOW THE STEPS WITHOUT ALL THE DETAILED DIRECTIONS SCROLL TO BOTTOM OF THIS REPLY) I hope this is helpful. I detailed below how I resolved my issue step by step for those who prefer a detailed explanation. When I opened Steam after installing Mac OS Big Sur Beta for the public I couldn't play my game.
