Hi Noel,
Welcome to the forum! I hope you find your time here useful and fun!
I'm not an expert by any means, but maybe your first, and easiest option might be to check all the connections into the back of your PC, and monitor. Make sure they are all fitted nice and tight.
The three beeps are a signal from your motherboard that something is wrong (but I expect you gathered that!), which could mean opening your PC case, and checking things inside, but check back here again this evening, and hopefully one of our more techie people will come to your rescue!
One question: you said nothing shows on your monitor? Are you saying it doesn't even power on?