#1 - Aug. 5, 2014, 5:23 p.m.
Once the zone is open, Nexus-Lord Donjon Rade (in Stormwind, Orgrimmar, Shattrath, Dalaran, Vale Shrines, or your garrison) will have a chat option to teleport you into Highmaul. Assemble your group, set the raid difficulty to Heroic, and then use that option to enter. The first person to zone in may end up in the wrong spot (have them re-zone), but once people are starting in the correct spot atop the hill in Highmaul, proceeding straight ahead into the citadel should lead you to Ko'ragh.
In your posts, please note your group size and makeup (high-end guild group, PUG, multi-guild team, etc.). Uploading and linking to a log parse at Warcraft Logs, or any similar site that can handle 6.0 logs, would also be quite helpful.