You need to gain access to Kiloude City. If you can't, go to the Lumiose Station over at the North Boulevard & talk to Sycamore in here, & he'll give you the pass card needed to take the train to get to there.
Then, head straight past the Pokémon Center until you're forced to turn north at a bend. Keep heading north from there & you'll find the friend safari to the right.
I'm not sure I really want to get into it. I've really got no real interest in using the friend safari right now. I'm also pretty sure I don't have access to the friend safari if I had to unlock it somehow to begin with. |D