There are several ways:
1) Go to Manage => Punches, and in the Filter section, select Status=Overridden. When you open an override punch, expand the Advanced section, and you'll see who overrode it and what the original times were (if they were edited from clock punch)
2) Go to Reports => Audit Trail, and select your filter criteria. To see original times, hover over any column title and select to show In Orig and Out Orig.
3) Go to Reports => Time Cards, and select your filter criteria. Added punches will have a red 'A' next to them, and edited punches will have a red 'E' next to them.