Go to Castelia City. There is a building with 11 floors in it. Go to the 11th floor, and search: you must find Rest.
As for Sleep Talk, unfortunately, you don't get the chance to get it for any of your Pokémon ; not by TM because TM Sleep Talk does not exist in Gen V and nor by tutor move, assuming you play Pokémon White.
Source, and for Sleep Talk, my knowledge as having beaten the whole game, with every TM and HMs. Hope this helps !