The obvious first question would be… do you have keyboard use to tap F2 and access the BIOS?. If you can access the BIOS, set it to boot from the CD/DVD drive following the instructions here: How to Set BIOS to Boot from CDROM
Another option is to press the appropriate key during the BIOS post. Right after you turn the computer on, when the BIOS post appears on the screen, press the Pause/Break key as necessary so you can read which key to use to boot directly from the CD/DVD drive without previously setting the BIOS for CD/DVD boot
If you don’t have keyboard use to access the BIOS, you may have to use a USB keyboard to complete the repairs or installation, read this: Keyboard and mouse don't work on startup...how do I fix?