I had the free "find my iPhone" app. I've lost I had the free "find my iPhone" app. I've lost my phone and don't know how to search for it phone and don't know how to search for it

Unless your phone was running iOS 5 or higher and you had created an iCloud account on it and turned on Fiind My iPhone before losing it, you won't be able to track it. (The Find My iPhone app doesn't enable Find My iPhone; it's only used to locate other devices that are lost that have it enabled in thier settings.)

If you did enable it, and it is turned on and has a connection to the internet, you can go to icloud.com, sign into your iCloud account, and track it as explained here: http://help.apple.com/icloud/#mmfc0f2442.