If you are doing an upgrade you can put the DVD in the drive and when it auto plays just follow the prompts to do the installation. Just make sure to pick upgrade for the installation type.
If you are doing a fresh/clean installation you can boot from the DVD and it should automatically start the setup. Make sure you computer is set to boot from the DVD drive before the hard drive.
Follow the prompts and the only thing you will have to be concerned about is where you are going to install Windows and what you are going to do with the hard drive. If you already have Windows on the drive and want to keep your files then make sure to back them up first.
If you like you can format your hard drive when it asks to wipe everything out and start clean. Or if its a blank hard drive you will have to format it to make it usable. Keep in mind that formatting will erase everything on it. If it is already formatted then you can leave it as is if you like.
After it formats and copies the necessary files it will take you through the graphical portion of setup where you will enter information such as your name and product key. You can basically accept the defaults for all the selections.
When its finished you will have to make sure that all your hardware has working drivers for it. Go into Device Manager and look for problems.
If your computer is working now I would go into Device Manager before the installation and make a note of what hardware you have. You only really need to worry about display adapter, network adapter and sound card. This way if you have to look for drivers online for your computer you will know what to search for.