OS X El Capitan: Delete files and folders
At any time, you can get rid of files, folders, and other items that you no longer need. You start by dragging items to the Trash, but the items aren’t deleted until you empty the Trash.
Delete an item from your Mac
Drag the item to the Trash. Or select the item, then press Command-Delete.
Do one of the following
Empty all items in the Trash: Click the Trash, then click Empty. You can also choose Finder > Empty Trash.
When you see a warning message, click Empty Trash.
Delete a selected item in the Trash: Control-click the item you want deleted, then choose Delete Immediately.
When you see a warning message, click Delete.
Delete a locked item from your Mac
You must unlock the item before putting it in the Trash.
Select the item, then choose File > Get Info or press Command-I.
If you are not logged in as an administrator, you may need to click the lock icon , then enter an administrator name and password.
Click the Locked checkbox to deselect it.
Drag the item to the Trash, click the Trash, then click Empty. You can also choose Finder > Empty Trash.
When you see a warning message, click OK.
Prevent the Trash warning message from appearing
Once: Press the Option key when you click Empty or choose Empty Trash.
Always: Turn off the warning in the Advanced pane of Finder preferences. Choose Finder > Preferences, click Advanced, then deselect “Show warning before emptying the Trash.”
If you change your mind before emptying the Trash
Click the Trash to open it, then drag the item out of the Trash, or select the item and choose File > Put Back.