On September 25, 2012, World of Warcraft opened its 4th expansion, "Mists of Pandaria". Pandaria is a continent located in the South Central portion of the World of Warcraft map.
To access Pandaria at level 85, simply go to your faction's main city -- Stormwind for Alliance or Orgrimmar for Horde -- and you'll receive a quest chain upon entering the city that will send you on to Pandaria and the Jade Forest. Once you reach the first encampment in the Jade forest, you'll see a portal that leads back to your faction's main city.
The quest chain doesn't take long to complete, but you will want to have 15 minutes or so in order to complete it given it is one of those roller-coaster ride events -- meaning there is no place to hop out of the chain once you get rolling in it.
When you arrive in Pandaria, you'll begin your long trek toward level 90. The quest flow is very linear and you'll rarely be puzzled as to where to go or what to do next. If you are a gatherer (Mining, Herbalism, Skinning), Jade Forest is rife with nodes. Be sure to take the time here to gather as they may be on an increased spawn rate due to the number of players in the zone. That way you won't outlevel the node-type as you move on to other zones.