calwred A Steam install can only be repaired through Steam. The option is called "verify integrity of game files" and is under Properties > Installed Files. Repairing will give you the updated version of Sims 4, so if it goes through, you don't need to do anything else.
You don't need to run the EA App as an admin for this process, but if you want to do so at some later date, you can find the executable here:
C:\Program Files\Electronic Arts\EA Desktop\EA Desktop
Right-click EADesktop.exe to see the "Run as administrator" option.