first off, lucky eggs are a held item in pokemon oras. they cause the holder to gain extra experience after defeating a pokemon.
go to an area where pelippers are found bring a pokemon that knows thief or covet or some poke balls.
run around the area with the dex nav on until a pelipper appears. check if it show if it has a lucky egg as a hold item. if it doesnt keep running around until you find the right one
now that youve found the right pelipper catch it or use the move covet/thief and take the lucky egg off it.
now you can use lucky eggs to train your pokemon faster