You can easily turn this on with a simple setting.
Windows uses a small registry setting for this, which basically tells the system to show seconds on the clock. The path is:
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
and the value ShowSecondsInSystemClock = 1 enables it.
If you manage PCs centrally, there’s also a Group Policy option called “Show seconds in system clock” under Start Menu and Taskbar, which does the same thing without manual edits.
Just keep in mind this is a per-user setting, so it applies to whoever is logged in. After enabling it, users may need to sign out or restart Explorer before the seconds appear.