Open Opera and click "Tools." Select "Delete Private Data." A pop-up window will open.
Click "Detailed Options" to display a list of items that Opera can delete. These include cookies, bookmarks and passwords. Beside each item is a check box.
Clear all check marks from all boxes. This will ensure that you do not accidentally delete history items that you do not want removed.
Click "Clear history of visited pages" to select it. Press "Delete" and Opera will clear the address bar's history.