To Close a Lead:
Once Leads are closed, you can search for them on the Leads Main Section Overview page in the "Advanced Search" area by selecting "Closed" in the "With Status" field.
Need to change your "Close Lead" reason?
You can add reasons easily! First, click Settings, then under "Application" select "Auto-Archiving Events & Closing Leads". From there you can click the "+" sign to add more reasons. They will then show up when you are ready to close a lead or event!