Breeding season is around February to July.
There is a chance that Corns will breed outside this time (I once had eggs in November from a new arrival) but the chances are better during breeding season as the female's more likely to be ovulating and receptive.
You don't have to do anything special to get them to mate. Just keep putting them together from February onwards and usually, you'll get a successful mating in the end. Putting the male in with the female shortly after she sheds is a good way of getting him interested.
The female has to be in good physical condition for breeding as egg formation and laying is very demanding. This means having good muscle tone, rather than being big because she's been fed a lot. The old guideline of "3 years old, 300g, 3 feet long" is going out of favour at the moment as being a bit conservative. However, combined with the muscle tone indicator I still think it's a reasonable view if you're planning your first season. You can start tweaking the boundaries once you're used to the process (which can be pretty hair-raising if it really knocks the stuffing out of your females).
