You shouldn't be going anywhere near a command prompt. You simply need to put the disc into its drive and restart your computer (assuming, of course, that you've got the BIOS correctly configured)
However, having got to a command prompt, type d: and press Enter. (That assumes that your disk drive is configured to be D. If it's got a different letter then obviously amend that instruction accordingly)
Then type dir and press enter. That will show you the files on the disc.
Then type the name of the file you want to run (which might, for example, be something like setup.exe) and press Enter again.