#1 - Aug. 8, 2014, 8:58 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. An exciting journey through the Foundry awaits you - you'll want to take the back-right path from the entrance (past Darmac's room), towards the depot at the end of the hall, and then take a sharp right and take a leap of faith down the abandoned elevator shaft.
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.