Warlords of Draenor includes a Level 90 Character Boost for one character on the upgraded game account. If you want to purchase a Character Boost without the expansion, the service is available in the WOW power leveling.
After you get a Character Boost for your account, whether it’s the boost included with Warlords of Draenor or through the World of Warcraft Shop, you’ll see the option to boost a character when you log into the game and visit your character selection screen.
The Level 90 Character Boost icon will appear near the top of your character list. When you click it, the game will walk you through boosting a character and choosing their talent specialization.
After boost a character to 90, they’ll receive a set of spec-appropriate gear, a set of bags, and some gold to get started. Any gear the character already had will be moved to their bags. If there isn’t enough space in their bags, their old gear will be mailed to them instead.