You can't
Its impossible, legendary Pokemon are unable to reproduce.
Every living thing has a way to reproduce. The 'genderless' tag on Pokemon in the games is to prevent players from breeding legendary Pokemon. That way, unless you traded (or cheated), you could not have more than one as it would contradict with the game lore. However, even in the anime it is shown that legendary Pokemon have the ability to reproduce and have young.
Unfortunatley.. they cannot because Heatran is a legendary. The GameFreak creators made it so you cant reproduce legendary pokemon. But, it would be fun to have an army of them:)
It is a rare pokemon, but it is not a legendary pokemon
Unknown is not a legendary Pokemon but it is considered rare. Legendary Pokemon are one of a kinds.
no lileep is not a legendary pokemon but it is an ancient pokemon
With the exception of Manaphy, legendary Pokemon do not reproduce, and will be unable to mate with Groudon. Even with Manaphy, the offspring is a different Pokemon (Phione) there is no way to duplicate them through breeding.
The legendary is palkia
No, snover is not a Legendary Pokemon
Azelf is a legendary Pokemon.
No, Blastoise is not a legendary pokemon.
Noivern is not a Legendary Pokemon.