You can talk to the sailor in Canalave city and ask him to take you to Iron Island. Go
into the cave and find PKMN trainer Riley. He will come with you through the dungeon. Get
tho the end, battle the Galactic Grunts and talk to Riley. He will thank you and ask if
you want an egg that he has. Be sure to have an empty slot in your party so you can take
the egg. Hatch the egg, and out comes Riolu, the Basic form of Lucario. Riolu evolves if
it is maxed-out happy, so level doesn't affect whether it evolves or not.
Good Luck!