The trashcan is located on the right side of the dock. If you want to delete a file from the hard drive, just drag the file to the trash. Release the mouse over the trashcan and you should here a sound and the icon will change to a trashcan with litter inside indicating a file is in the trash. To retrieve a file that may have mistakenly been added to the trash, double click on the trashcan and the items inside will show in the finder. Simply drag the item(s) you want to keep to a folder and those items will be removed from the trash. Items in the trashcan stay in the trash until the trashcan is emptied.
Note: the trashcan is also used for other functions. The trashcan icon will turn into a nuclear icon when one drags a blank CD to burn. Keep this in mind when looking to burn various disks.