I need help with a 2007 Excel spreadsheet?

I am a complete and utter novice at Excel, and I have a spreadsheet that was designed for me to keep track of unpaid balances (at work). Each time I print a report in our internal software, I compare accounts to what’s already been entered in the spreadsheet to prevent duplication, and I’ve doing that comparison manually by scrolling up the list and looking. But the list is getting extensive, and I suspect there’s a way to “search” for an item within the spreadsheet, I just don’t know how.

Did I manage to express my question at all clearly? Is there a way to see if an item is already present in a spreadsheet? Can you teach me how?