If the monitor says no signal, it means that either your cable isn't connected, could be damaged, check the pins on the cable and see if any of them are damaged. Lastly if could also be the PC isn't powering on properly, if the computer itself isn't on and sending out a video signal, there is no signal for the monitor to receive. If it's the PC itself, try checking for any indication to determine if its turning on or not. For example: do you hear any fans, hard drive trying to spin up, beeps, usually signals from motherboard if there is an issue. If there are beeps you can google the particular pattern you hear and can find information on what's going wrong.
But most importantly, why are you doing this? do you want to learn to fix and old PC or simply learn linux? If you are interested in just learning linux, you can save yourself time and money by either buying a rasberry pi or even better, running linux on a virtual machine. Virtualbox from oracle or Vagrant Cloud from Hashicorp are both free and pretty good ways to run linux inside of another computer when you need it and turn it off when you don't as easy as closing an application.