deleted the hard drive when trying to wripe all data so now try to reboot from disc but just have an apple on the screeb abd not sure if the computer is doing anything
So, is the hard disk empty with no OS on it? If so, hopefully OSX Internet Recovery will work:
http://support.apple.com/kb/HT4718 (Command+Option+r should start the process)
If your using a wireless keyboard it is most likely unpaired from your iMac and you will need to use a USB keyboard for Startup key combinations.
Retrieving data ...