Summarize:

If you don't already have a Honedge, don't worry — they're not especially hard to find in Pokémon X and Y. You'll want to look in Route Six, which is the area connecting Route Seven to the Parfum Palace. Route Six is marked by two rows of shade trees along the sides of a central path. However, to find Honedge, you need to get to the tall grass behind the trees, which means entering the palace grounds and immediately exiting through one of the side paths.  Note that Honedges appear approximately 15% of the time in the tall grass. You will probably have to fight a handful of Oddishes and Sentrets before you encounter a Honedge.  It's also possible to get Honedge in Alpha Sapphire/Omega Ruby. However, this can only be done through trading. You can't catch Honedge in the wild in these games. There isn't a special strategy to catching the Honedges in Route Six. Once you get into a fight with one, get it down to a low HP level (without making it faint) and throw your best Pokéball at it. The Honedges you will encounter will be about level 11 or 12, so the fight shouldn't be too difficult. However, here are some things you may want to know:  Honedges are extra-weak versus ghost, fire, ground, and dark type attacks. Honedges are immune to normal, fighting, and poison type attacks. Honedges take normal damage from water and electric type attacks. Honedges take reduced damage from every other type. There's nothing out-of-the ordinary about the way you must level up your Honedge — just keep training it slowly and steadily. Since you'll catch your Honedge at about level 11 or 12, you have about 23 or 24 levels to gain until it will evolve. This can take some time, but it will be a little faster if you use experience-boosting items like:   Exp. Share: This item gives experience to all the Pokémon in your party — not just the ones that participate in the battle. You can get the Exp. Share from Alexa in Santalune City after defeating Viola.   Lucky Egg: The Pokémon that holds this item will receive 150% of the normal experience it would get from battle. You can find the Lucky Egg several places: You can show the girl in the girl in the Coumarine City hotel lobby a Pokémon with a high friendship level You can get it from beating Graffiti Eraser level two in the PokéMileage Club.f You can get it from wild Chanseys in the Friend Safari Once you get your Honedge to level 35, it will start to evolve into Doublade. There aren't any time or item requirements to get it to evolve — evolution should happen automatically.
Find a Honedge in Route Six. Catch the Honedge. Train the Honedge to Level 35. Allow it to evolve.