"Operating system not found"

When my system reboots I get "operating system not found" My IBM thinkpad has been completly formated. I also get a red box that reads "hard drive not installed. Physically the hard drive is in. I need to know A- How to install operating system. B-How to install/fix hard drive. And C- How to Get computer to read all drives/create (C) drive. Have some idea's but I am not a professional and I am afraid to screw it up more than I already have. Could I get some professional advice on how to continue the proper way?