I haven't seriously tried breeding goldies myself, but I do know a lot about it in theory
There are several different ways to breed goldfish, for example you could hand breed them, but that takes experience or you may hurt the female and give her "cracked" ovaries (in the lack of a better word). So for you, I'd suggest trying to spawn them in your pond!
Introduce a pair in the warmer part of the spring, before the summer heat, the change in temperature might trigger spawning behavior. Feed them a lot of live foods whenever you can, and hope for the best
After you've noticed eggs being laid, it might be good to take the parents away from the pond and let the fry develop in peace. The parents might otherwise eat all the eggs.
Another way would be setting up a breeding tank, just be sure that the filtration is gentle, a simple sponge filter will do, you could even put it together yourself!
An airstone will be needed too, the circulation in the tank needs to be good, otherwise the eggs might catch fungus. You could easily make a spawning mop for that purpose! Take some green yarn and wrap it around a book, then cut off one end and tie the other. It should look much like a mop c: Tie some cork to the tied end so that it'll float on it's own! The goldfish need to be prepared with live foods and warmer temperatures again, and then introduce a pair into the tank
They should lay eggs on the mop at some point, so take away both the fish when you're certain that the eggs have been fertilized
Goldfish lay their eggs at the break of dawn usually, so it's good to be waking up earlier for a few days to be sure that you'll catch the eggs before they get eaten
If you want to, you could keep the female separated for a couple of days after they've laid eggs so that she can rest up. Remember to feed the fry the first time after the yolk sac has been absorbed! Before that, they don't even have mouths, so it'd be a waste to try to feed them with anything c:
That's pretty much it, hope you'll get some goldfish babies!