The procedure will be documented in your user guide. If you lost it, you can download it from your manufacturer's web site. One thing that's worth a try would be to insert the first disc and see if you can boot from it. That often (but not always) works.
When you've gotten your system back like you want it, I urge you to get yourself an external hard drive and a good 3rd party backup program. You can set it up to do everything automagically at the time and frequency of your choice. 1 TB external hard drives are about $70 these days and a really good FREE backup program is the Easeus Todo Backup Free which you can download from
http://www.todo-backup.com/products/home/free-backup-software.htm . That can save you a lot of time and frustration the next time something like this happens. Sooner or later it happens to all computers for one reason or another.
When I purchased my computer I did as advised and made a backup copy of my computer as directed. The Hard Drive recently went bad. I have purchased a identical new hard drive. Now how do I use my cd's to install what was on the old Hard drive?