Blizzard has released a detailed blog post on the Creation Catalyst, which releases next week on April 12th (NA) / April 13th (EU), and includes information on some frequently asked questions.
Blizzard Greetings! The Creation Catalyst will become available to players after scheduled maintenance the week of April 12. To access it, you will travel to the far south area of Zereth Mortis that is the Catalyst Gardens.The Creation Catalyst is on a floating island above the main pool area and can be reached via flying or using a small teleporter right below it. At a base level, how it works is you input a piece of Season 3 gear and a corresponding tier set piece will be made with a matching item level.
The useable items can be Season 3 gear from raids, Mythic+, PvP, World Boss Antros, or items purchased with Sandworn Relics from Rafiq in Pilgrim’s Grace, Zereth Mortis. The applicable slots are helms, shoulders, cloaks, chests, bracers, gloves, belts, legs, and boots.
Note that the 2-piece and 4-piece set bonuses will only be on the helms, shoulders, chests, gloves, and legs. The Creation Catalyst can transform one item per week, but it can store up these charges so that if you miss a week you’ll be able to create two set pieces the following week, and alts or players who come along later in the Season may be able to create an entire set if they have the Flux for it.
The Catalyst will use the Cosmic Flux currency that is earned from a wide variety of activities in the game. The costs for the different item slots are:Bracers and Cloaks: 600 Belts and Boots: 800 Gloves and Shoulders: 1200 Chests, Helms, and Legs: 1500 If a character vendored, disenchanted, or destroyed a Season 3 item that you want to use for this system,.
Read more on wowhead.com